
































































































































































































































































































































































ON 




FIELD FORTIFICATION, 




CONTAINING 




\\ S 


f INSTRUCTIONS ON THE METHODS OF LAYING OUT, 
CONSTRUCTING, DEFENDING, AND ATTACKING 













INTRENCHMENTS, 




WITH THE GENERAL OUTLINES ALSO 
OF 



THE ARRANGEMENT, THE ATTACK AND DEFENCE 




OF 


PERMANENT FORTIFICATIONS. 







BY D. H. MAHAN, 


Pro feat or of Military and Civil Engineering in the United States 





Military Academy. 

U * 

fl O 

> > > 

} > 

HIED EDITION, REVISED AND ENLARGED. 

NEW YORK: 

N WILEY, 56 WALKER ST. 





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. 

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f f ;» V f ' 


Entered according to act of Congress in the year 1836, by 
WILEY AND PUTNAM, , 
in the Clerk’s Office of the District CoHrt of the Southern District 
of New York. 

:/^ & r *.. . ’. ... 


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TO 


THE OFFICERS OF MILITIA 

OF 

THE UNITED STATES. 


Gentlemen:— 

That an efficiently organized Militia is the firmest and 
only safe bulwark of the State, is a political axiom admitted by 
all who understand the natnre of our free institutions. What¬ 
ever, then, may contribute, in any degree, to strengthen this arm 
of our national defence, it is to be hoped will meet with an 
indulgent reception from those to whose province it falls to 
instruct, discipline, and lead it into action. Feeling a strong 
conviction that its efficiency must depend upon sound element¬ 
ary military knowledge, I have presumed to dedicate the follow¬ 
ing work to you, Gentlemen, in thelhope that it may be found 
useful to our country, by proving serviceable to yourselves. 
Should this, my chief aim, be accomplished, I shall receive the 
highest gratification, in being thus enabled to make some return 
to my country, for the benefit which she has conferred on me 
in an education at our only National School. 

With sentiments of high respect, 

I have the honor to be, 

GENTLEMEN, 

Your obedient servant, 

D. H MAHAN 

United States’ Military Academy, ) 

West Point. \ 


I 



NOTICE 


O’ This Work will be speedily followed by 
“Instructions on Out-Post and Detachment 
Duties of Troops,” drawn from the latest and 
most reliable Military Writers, intended for the 
use of Subaltern and other Officers of Volunteers 
and Militia. 



PREFACE. 


In preparing the work now laid before the public, 
which is chiefly designed for the use of the Cadets 
of the United States’ Military Academy, the aim of 
the writer was to make a book which should also 
be generally useful,—one that should contain all 
the principles and important details of that branch 
of the Art of Fortification of which it specially 
treats, developed in a manner to be within the com¬ 
prehension of any person of ordinary intelligence,— 
a book not for the study alone, but one which the 
officer can take with him into the camp, and consult 
at any moment. 

With respect to the contents, the writer has col¬ 
lected his information from every source within his 
reach; rejecting all unnecessary discussions, and 
admitting no results, which have not either been 
submitted to a rational analysis, or tested by fair 
experiment; preferring, in all cases, the views of 
persons who wrote from their own experience, to the 
conjectures of others whose theories, however plau¬ 
sible, rested on a less solid foundation. 

In arranging the matter, the writer has endea¬ 
vored, as far as it was practicable, to confine the 
text to the principles alone, reserving the minor 
details for the plates, and the explanations appended 



vi 


PREFACE. 


to them; and on this point he would hazard one or 
two remarks. 

Much that appertains to the Engineer’s Art is 
but an affair of feet and inches ; facts which are 
the results of long usage, holding, in many in¬ 
stances, the important position of principles. His 
experience has taught him that those authors are 
the clearest who enter into the minutiae of their 
subject; and that with pupils of superior minds, a 
thorough knowledge of details is an invaluable aid 
in unravelling the difficulties, and retaining the 
principles of the Art; whilst, with those of limited 
capacities, a want of such detail leaves them with 
the most vague and unsatisfactory notions. 

Having said thus much of the plan of the work, 
a few words, respecting its object, may not be mis¬ 
placed. The importance of a knowledge of Field 
Fortification, to officers of all arms in the regular 
army, need not be insisted upon; the daily occur¬ 
rences of a campaign demonstrate this too clearly. 
To the militia officer, this knowledge is even of 
more importance than to the regular; for called 
upon, in many cases, to act without the co-opera¬ 
tion of regular troops, in the defence of his own 
fire-side, he will require all those conservative 
means which add strength and confidence to irregu¬ 
lar forces when brought for the first time before an 
enemy. 

To suppose irregular forces capable of coping on 
equal terms with disciplined troops, is to reason, 
not only against all probability, but against a vast 
weight of testimony to the contrary. It is not 
indeed that discipline confers individual courage; 
certainly a greater proportion of this essential 
military virtue will, in all cases, be found among 
the militia, composed as it must be of men of a 


PREFACE. 


vii 

nigher grade of moral and intellectual qualities, 
than is to be met with among the common soldiery 
of any country. But these men, with all the supe¬ 
rior advantages that must actuate the volunteer, 
necessarily want that indispensable element of suc¬ 
cess, in pitched battles, which results from disci¬ 
pline and habitual training. Called out on a 
particular emergency, with little or no previous 
exercise in the services they are required to render, 
militia cannot have that shoulder-to-shoulder cou¬ 
rage, by which men are animated, who have served 
long together, which begets a reliance on each other, 
and a confidence in their chiefs, and which is one 
of the surest guaranties of victory. But place the 
militia soldier on his natural field of battle, behind 
a breastwork, and an equilibrium between him and 
his more disciplined enemy is immediately esta¬ 
blished ; with a feeling of security in his position, 
his confidence in his own exertions is restored ; 
with a full certainty that his enemy cannot close 
upon him, before he can retire beyond his reach, he 
does his duty coolly, and with an execution so terri¬ 
ble, as to have placed the achievements of our mili¬ 
tia, from the day of Bunker Hill, to the dosing 
scene of our last war at New Orleans, on a line with 
the most brilliant military exploits of the best disci¬ 
plined troops in the world. 

But were not these reasons in themselves suffi¬ 
cient, others of greater cogency could be adduced, 
in favor of intrenched positions for militia. Its 
ranks are filled with all that is most valuable in so¬ 
ciety. The farmer, the mechanic, the merchant, 
the members of the learned professions, must all 
quit their peaceful avocations to meet the foe. The 
father of the family jeopards its future prosperity, 
the son exposes his widowed mother to the chances 


PREFACE. 


• • • 

Vlll 

of an old age of penury, to bare their breasts to a 
mercenary band, without other home, without other 
ties, than the camp affords. Surely nothing but a 
reckless disregard for the best interests of society 
could urge men, under such circumstances, to 
forego the advantages of every possible conservative 
means. 

The chapters of the work on Military Bridges, 
Reconnaissances, and Permanent Fortification, are 
necessarily incomplete. A full discussion of these 
subjects did not come within the limits of the 
writer’s plan. The Military Art, in all its branches, 
is founded upon a comprehensive and thorough 
knowledge of the exact and physical sciences; and 
in no one branch is the importance of this know¬ 
ledge more felt, than in that of Engineering. In 
adding, therefore, these chapters, a clear compre¬ 
hension of which supposes an advanced state of 
scientific attainment in the reader, it was far from 
the writer’s intention to lead his fellow citizens into 
error, by spreading a knowledge necessarily of a 
superficial kind amongst them ; but he rather hopes 
it may serve the purpose of fixing their attention 
more strongly and minutely upon a profession, 
which requires the season of youth to be spent in 
thoroughly acquiring its elements, and the devotion 
of mature age to an incessant study of its princi¬ 
ples, and their applications. 

The author is indebted to Lieut. J. E. BLAKE , 
6lh Infantry, for the very correct and handsome 
execution of the original drawings , from which the 
plates were engraved. 


TABLE OF CONTENTS 


INTRODUCTORY CHAPTER. 

On the Effects of Musketry and Artillery, and 
the means of directing their fire to 
obtain the best results, . . . xv 


CHAPTER I. 


Page 

Art. 1-2. Art of Fortification, . . . 1 

“ 3. Permanent and Field Fortification, . 1 

“ 4. Intrenchments, ..... 1 

“ 5-7. General Conditions of Intrenchments, 1 

“ S. General form of the Profile, . . 2 

“ 9. General Arrangement of the Plan, . 3 

“ 10-11. Flanked Disposition, . . 4 

** 12. Dead Angle, ..... 4 

“ 13. Sector without Fire, ... 4 

“ 15. General Outline of the Attack of In¬ 
trenchments, .5 

“ 16. General Measures for the Defence, . 5 

“ 17. General Principles of the Plan and Pro¬ 
file, . . . . . . 6 


CHAPTER II. 


Art. 

18. Site, Command, and Relief, 

. 11 


19. Line of Direction of Fire, . 

. 11 

cc 

20. Directing Line of the Plan, 

. 11 

<< 

21. Elements of Intrenchments, 

. 11 

<< 

22. The Redan, .... 

. 12 

a 

23. The Lunette, .... 

. 12 

t€ 

24. The Cremaillere, 

. 12 

(( 

25. The Priest-Cap, .... 

. 12 

€€ 

26. The Redoubt, 

. 12 






X 


CONTENTS. 


Pag* 

Art. 27. The Star Fort,.13 

“ 28. The Bastion Fort, .... 14- 

“ 29. Relation between the extent of In- 

trenchments and the Troops for their 
defence, ..... .16 

“ 30. Conditions that a Field-Fort should 

satisfy, . .... 17 

CHAPTER III. 

Art. 31. General Dimensions of the Parapet, . 18 

“ 32. Command of the Interior Crest, . . IS 

“ 33. Thickness of the Parapet, . . .19 

“ 34. Inclination of the Superior Slope, . 21 

“ 35. Inclination of the Exterior Slope, . 21 

“ 36. Inclination of the Interior Slope, . 21 

“ 37. Tread of the Banquette, . . .21 

“ 38. The Berm,.22 

“ 29. General Dimensions of the Ditch, . 22 

“ 40. Slopes of the Scarp and Counterscarp, 23 

“ 41. Approximate method of regulating the 

dimensions of the Ditch, . . 23 

CHAPTER IV. 

Art. 42, 43. Influence of the Site on the Plan 

and Relief,.24 

“ 44. Defilement from a Direct Fire, . . 24 

“ 45-48. Defilement from a Reverse Fire, . 25 

“ 49-51. Method of determining the dimen- 

♦ sions of the Traverse, for Reverse 

Defilement,.28 

“ 52. Defilement of Enclosed Works, . . 30 

“ 53 General Remarks on the Defilement 

of Works,.30 

CHAPTER V. 

Art. 56,57. Method of Profiling, . . .32 

“ 60. Estimate of the daily labor of a Man 

working on an Intrenchment, . . 33 


CONTENTS. 


XI 


Pag« 

Art. 61. Distribution of the Working Parties, . 33 

** 62-64. Manner of forming the Excavation 

and Embankment, . . . .33 

“ 65. Precautions to be taken in stony soils, 34 

“ 66. Drainage of the Terre-Plein, . . 34 
“ 67. Time required to construct a work, . 34 


Art. 

CHAPTER VI. 

68, 69. Revetments, . 

• 

36 

ii 

70-72. Sod Revetment., 

• 

36 

ii 

73, 74. Pisa Revetment, . 

• • 

37 

H 

75-79. Fascine Revetment, 

• • 

37 

ii 

80. Hurdle Revetment, 

• • 

39 

ii 

81-83. Gabion Revetment, 

• • 

39 

ii 

84. Plank Revetment, 

• • 

40 

ii 

85. Sand-bag Revetment, . 

• • 

40 

ii 

86-99. Timber Revetment of the Ditch, . 

41 

Art. 

CHAPTER VII. 

100-4. Remarks on Obstacles on 

the Exte- 



rior, .... 

• • 

43 

(( 

105. Artificial Obstacles, . 

• • 

44 

(( 

106-8. Troups-de-loup, 

• • 

44 

ii 

109-11. Abattis, 

• • 

45 

ii 

112-14. Palisades, . 

• • 

45 

ii 

115-16. Fraises 

• • 

46 

a 

117. Stoccades, 

• • 

47 

a 

118-20. Chevaux-de-frise, 

• • 

47 

a 

121. Small Pickets, . 

• • 

48 

a 

122. Crows-feet, 

• • 

48 

a 

123-26. Artificial Inundations, 

• • 

48 

a 

127, 128. Mines, 

• • 

49 


CHAPTER VIII. 

Art. 129, 130. Interior arrangements for the 

Defence, . . . .51 











CONTENTS. 


Pag® 

Art. 131, 132. Armament of Musketry and Ar¬ 
tillery, .51 

“ 133, 134. Remarks on the employment of 

Artillery, . . .52 

“ 135. Batteries, .... .52 

“ 136-39. Barbette Battery, . . 52 

“ 140-47. Embrasure Battery, . . .54 

“ 148-53. Platforms, .... 56 

“ 154-61. Powder Magazines, . . 58 

“ 162. Traverses, . . . . .59 

“ 163-65. Enclosures for Gorges and Outlets, 60 

“ 166. Outlets,.61 

“ 167-69. Barriers,.61 

“ 170. Safety Redoubt, . . .62 

“ 172-85. Block-houses, . . . .62 

“ 186-92. Ditch Defences, . . . .66 

CHAPTER IX. 

Art. 193. Classes of Lines, . . . . 69 

“ 194. Principles regulating the Plan of Lines, 69 

“ 195-205. Continued Lines, . . .69 

“ 206,207. Lines with Intervals, . . 72 

“ 20S-11. System of General Rogniat, . . 73 

“ 212-15. General Observations on Lines, . 74 

CHAPTER X. . 

Art. 216-23. Intrenchments of Mountainous 

Sites,.76 

“ 224. Intrenchment of Forests, . 78 

“ 225. Intrenchment of Marshes, . . 79 

“ 226-36. Intrenchment of Rivers, . . 79 

“ 237,238. Intrenchment of Villages, . . 82 

“ 339-41. Military Posts, ... 83 

“ 242,243. Arrangement of Hedges for De¬ 
fence, . .85 



CONTENTS. 


• • • 
3QU 

Page 

Art. 244-47. Arrangement of Walls for De¬ 
fence, . . . . .86 

“ 248, 49. Barricades,.86 

“ 250-56. Defensive arrangement of Houses, 87 

“ 257-65. Military Positions, . . .89 


CHAPTER XI. 

Art 266-68. Operations preliminary to the At¬ 
tack of Intrenchments, . . 92 

“ 269-73. Attack by Surprise, . . .93 

“ 274-87. Attack by Open Force, . . 95 

“ 288-99. Measures to be taken in the De¬ 
fence, .99 


CHAPTER XII. 


Art. 300-2. General Observations on Water- 
Courses, &c., . . . . 

“ 303, 304. Reconnaissance of the Locality 

for a Bridge, . 

“ 305-8. Floating Military Bridges, 

“ 309-18. General Observations on Boat- 

Bridges, . . . . . 

“ 319-38. Construction of the Bateau Bridge, 

** 339-41. Operations in breaking up the 

Bateau Bridge, 

“ 342-45. Bridges constructed with ordinary 

boats, . . . . . 

“ 346-56. Construction of Raft-Bridges, 

“ 353-70. Flying Bridges, .... 

“ 371-77.'Trestle Bridges, . . . . 

“ 378. Temporary Bridges, . 

“ 379-83. Fords,. 

“ 384-87. Passages on Ice, . 

“ 388-99. Preservation and Destruction ©f 

Bridges,. 

“ 400-6. Passage of Rivers, 


104 

104 

105 

106 
109 

113 

114 

115 
118 
121 
122 

123 

124 

124 

127 


xiv 


CONTENTS. 


CHAPTER XIII. 


Pa*e 


Art. 407-22. Military Reconnaissance, 


130 


CHAPTER XIV. 

Art. 423-25. Permanent Fortification, . . 135 

“ 426-30 General Properties of Permanent 

Works, ..... 135 
“ 431-36. General Principles that Permanent 

Works should satisfy, . . 136 

“ 437-46. Description and Properties of the 

Outworks, .... 138 
“ 447-4S. Object of Interior Retrenchments, 140 

“ 449. Arrangement of the Crest of the Glacis 141 

“ 450. Object of Traverses in the Covered 

Way,.141 

“ 451. Communications of Permanent Works, 141 

“ 452. Relief and Command of the Outworks, 141 

“ 454. Uses of Counterscarp Galleries, . 142 

“ 455, 456. Uses of Case-mates, . . . 142 

“ 457. General Outline of the Attack of Per¬ 

manent Works, .... 142 
“ 496-505. General Outline of the Defence 

of Permanent Works, . . 152 

“ 506. Uses of Permanent Works, . . 156 

Note A. Relation between the Terre-plein and 

Interior Crest of the Square Redoubt, 16 1 
Note B. Method of Equalizing the Excavation 

and Embankment of a Field Work, 164 


INTRODUCTORY CHAPTER 


ON THE EFFECTS OF MUSKETRY AND ARTILLERY, 


AND THE MEANS OF DIRECTING THEIR FIRE TO OBTAIN 
THE BEST RESULTS. 


As the object of all defensive arrangements, 
whether artificial objects be raised, or the natural 
features only of a position be seized upon for the 
purpose, is to place troops under cover from the 
enemy’s fire, and to enable them to deliver their own 
with effect, some knowledge of the chances of hit¬ 
ting a mark of given dimensions at various distances, 
as well as the influences which the undulations and 
character of the ground, and the physical and 
mental state of the party firing, may have upon their 
aim, are essential elements in estimating the advan¬ 
tages which they present. The object of this intro¬ 
ductory chapter is to present, from the most recent 
and authentic sources, some of the facts arrived at 
by experiment , which beai on the question. 

I. Remarks cm Target Practice of Small Arms. 
There is no fact more striking than the great dis¬ 
proportion between the number of combatants put 
hors de combat and the amount of ammunition ex¬ 
pended, even in the most bloody engagements. 
Hundreds of instances might be cited in support of 
this. Military writers estimate that not more than 



XVI 


one ball out of ten thousand attains its mark; and 
it is estimated, for example, that in the Expedition 
of the French to Algiers, in 1830, which lasted but 
15 days, upwards of three millions of cartridges 
were consumed. The causes of this disproportion¬ 
ate application of means to an end, may be found 
partly in a careless use of his ammunition by the sol¬ 
dier ; partly in the want of good instruction and fre¬ 
quent practice, particularly in those men who have 
not been familiar with the use of fire-arms from 
their youth ; partly in the haste with which a fire 
against an enemy is delivered, wffiich destroys calm¬ 
ness and good order, and impairs the aim ; but chief¬ 
ly by the over estimation of distance caused by fear, 
smoke, and the moveable character of the mark. 

Much depends upon the attention to his duties 
paid by the officer to prevent this. The men should 
be frequently practised at target firing, and be 
taught to note the influence which the firmness 
with which the piece is pressed against the shoulder, 
its depression or elevation, according to the distance 
of the target and the character of the ground, both 
as to the hardness of its surface and its undulations, 
have upon the accuracy of the aim. This practice 
should not be confined to the open field, but be also 
extended to the various positions in which soldiers 
may be placed behind breastworks and other shelters, 
such as palisades, stoccades, loopholed walls, abattis 
.arranged for defence, &c., in order that the soldier 
may feel himself perfectly at home under all circum¬ 
stances, and not be called upon to cast about for the 
best way of managing his piece in every new emer¬ 
gency. So far from urging the men to load and fire ra¬ 
pidly, every pains should be taken by the officer to im¬ 
press upon them the necessity of not hurrying, of 
keeping perfectly cool, o' loading steadily and aiming 


XVI1 


deliberately. Volley firing is admirable practice for 
this purpose ; that by files is apt to give a slovenly 
and hurried action to the soldier. The fire of troops 
in line should be kept, as far as possible, under the 
control of the officer. His position and means of 
estimating distance enable him far better to judge 
of the proper moment than the men generally can. 
It is generally admitted that not more than four or 
five rounds can be fired in two minutes, allowing 
the men time to aim deliberately; three may be 
fired in one minute, but at the expense of a good 
aim. 

As all infantry now are instructed as well in the 
duties of skirmishers as in the ordinary service of 
the line, they should be practised at firing both at a 
small mark, like the ordinary round target, and at 
a large square one, with black bands made across it, 
showing the ordinary height of the knees, centre of 
the body, the breast, shoulders, head and top of the 
cap. 

As the point blank of the musket fired with the 
bayonet off is at about 120 or 130 yards, to attain 
a point at this distance, it must be directly aimed 
at; when it is at a distance short of this the aim 
must be below it; and when at one over this the 
aim must be above it. With the bayonet fixed the 
musket has no point blank, and to hit a point the 
aim must always be above it. 

The following rules for aiming are given by 
Robert, a recent French author of high standing, 
in a work on artillery, as drawn from the practice 
of the French. 

To hit the centre of the body, at all distances up 
to 110 yards, with bayonet fixed, aim at the breast. 

To hit the same point, from 110 to 150 yard* 
distance, aim at the shoulders. 


xvin 


To hit the same point, from 150 to 200 yards 
distance, aim at the head. 

To hit the same point, from 200 to 220 yards 
distance, aim at the top of the cap. 

To hit the same point, from 220 to greater dis¬ 
tances, aim according to circumstances. 

II. Probable Effects of Small Arms. Beyond 
220 yards the effect of the fire is very uncertain. 
Beyond 450 yards the ball seldom gives a danger¬ 
ous wound, although the musket, fired under an 
elevation of 4°, or 5°, will carry from 600 to 700 
yards, and under greater elevations over 1000 yards. 

The nature of the surface of the ground, as has 
already been stated, has considerable influence upon 
the efficacy of the fire. In broken, or ploughed 
ground, fire is less effective than on an even firm 
surface, since in the former the balls that strike it 
are embedded, whereas in the latter they ricochet, 
and thus attain their mark; it being estimated that, 
under favorable circumstances, about one-seventh 
of the balls produce their effect in this way. 


Table of effects of fire on a target 5 feet 9 inches 
high, and 95 feet in length. 


No. of balls out of 100 

Distance to the Target 

that hit the mark. 



in 

yards. 


On even ground by di- 

85 

170 

255 

340 

425 

510 yds. 

75 

50 

27 

20 

14 

7 

rect and ricochet shots. 

On broken ground by 







direct shots. 

67 

38 

16 

6 

3 

5 

Penetration into pine, 
&.C., in inches at same 
distances. 

3.3 in. 

2.2 

1.2 

0.7 

0.4 

0.1 

Do. into oak same 







distances. 

_____ 

4 in. 

2.3 

12 

0.6 

0.4 

0.1 


In rifle practice with the ordinary rifle, owing to 
the greater length of time requisite to load this arm, 















xix 


there is some compensation for the more uncertair 
aim of the musket in short ranges and large targets. 
When the distance is under 170 yards and the mark 
large, the effects of the two arms are nearly equal. 
But for distances of 220 yards, and beyond, the bal¬ 
ance is greatly in favor of the rifle. This superi¬ 
ority of the rifle is more particularly observable in 
the latest improvements of this arm, by Hall, in 
loading at the breach. 

Decker, a German author of reputation, lays down 
the following, as the probable number of balls out 
of 100 which will attain their aim, when fired by 
well instructed troops, making full allowance for the 
over-estimation of distances in firing on an enemy. 

Troops firing in line at 300 paces, out of 100 balls 1 will touch. 


a a 

200 “ 

it 

20 

it 

it a 

100 “ 

a 

40 

it 

“ as skirmishers 

400 “ 

u 

5 

it 

it it 

300 “ 

a 

10 

it 

a a 

200 “ 

« 

30 

it 

a a 

100 “ 

»« 

80 

it 

Rifle practice 

400 “ 

a 

10 

u 

a u 

300 “ 

a 

20 

g 

u a 

200 “ 

u 

72 

a 


The firing of skirmishers is the more effective 
from the greater deliberation in aiming and in seiz¬ 
ing upon the opportune moment. Volleys produce 
a tremendous staggering effect, by the simultaneous 
fall of numbers, when they are coolly thrown in at 
short ranges. To produce this effect they ought 
not to be delivered at greater distances than 200 
paces. 

Decker condemns file firing except for the pur¬ 
pose of occupying new troops when first brought 
before an enemy. 

III. Ranges and 'probable effects of Field Artillery. 
—In artillery practice, the greatest deliberation and 






XX 


coolness must be exercised to obtain good results, 
There are so many circumstances which affect the 
aim of artillery, that nothing but the most careful 
attention to the effects produced by the first few 
rounds will enable the officer to manage his guns 
with advantage. 

The point blank range of six pounder field guns 
is about 600 yards, and that of twelve pounders 
about 700 yds. The chances of hitting a mark are 
less with pieces of small than of large calibre, ow¬ 
ing to windage, the effect of wind, &c. The ranges 
of all calibres vary more when the pieces are fired 
under small angles of elevation than under large 
angles. 

The following Tables of the number of balls out 
of 100 which will attain a target 6 feet high, and 95 
feel in length, at various distances, is taken from 
Piobert :— 


Distances in yards. 

550 

870 

1300 

No. of 12 pdr. shot (French) out of 100 

57 

38 

19 

U 0 u u u u 

49 

32 

12 


Table of the number of balls out of 41 in a can¬ 
ister which attain a butt 6 feet high, and fifty feet in 
length. 


Distances in yards 

220 

440 

660 

12 pdr. canister (French) 

9 

9 

4.5 

g U l< (( 

8.3 

7.4 

4 


The usual diameter of grape is about one-third 
that of the ball. To produce a good effect at a dis¬ 
tance, grape ought not to be less than one inch in 
diameter. Smaller balls produce greatest effects at 
















XXI 


short distances. Grape of one-third the diameter 
of the ball has sufficient velocity at 880 yards with 
12 pounders, and 760 yards with 8 pounders, to dis¬ 
able men. Whe.i the distance is within 500 yards, 
the fire of grape is superior to that of ball against 
troops. 

In howitzer practice the shells are fired with 
small charges, as they break easily when they 
strike an obstacle with a great velocity. The point 
blank of the howitzer varies with the charge. The 
greatest range of the twenty-four pdr. howitzer is 
about 2200 yards ; that of the six inch about 2600 
yards. 

The chances of hitting a mark with the howitzer 
diminish with the length of the bore, the calibre and 
weight of the shell. The deviations with small 
charges are nearly double those with heavy charges. 

The shell of the howitzer produces no effect when 
fired against masonry, as it invariably breaks. It 
imbeds itself in earth and wood, and bursting pro¬ 
duces a considerable crater. The fragments of the 
shell are often thrown to distances over 600 yards, 
and they do great damage to objects near. The 
wounds from them are very dangerous. The shells 
loaded with incendiary composition are used to fire 
buildings. 

The rate of firing for field guns is from 35" to 
40" for six pdrs., and one minute for twelve pdrs. 
But when the enemy is close at hand, and deliberate 
aim not necessary, two rounds may be fired per 
minute. 

IV. Selection of positions for field batteries. 
The position taken up on the field for a battery 
must be looked at in a double point of view. 1st, 
as to its suitableness for annoying the enemy and 


xxii 


2d, as to its being favorable for limiting the effects 
of the enemy’s fire aimed at the battery. 

As a general rule artillery should overlook all the 
ground over which an enemy might advunce, the 
pieces of heaviest calibre being placed on the most 
commandiiig points. The batteries, however, should 
not be within musket range of w’oods, or of any 
ground where the enemy’s sharpshooters might find 
cover to annoy them. The slope of the ground on 
which the gun rests must not be too oblique to the 
line of fire, otherwise the shot will not tell; the de¬ 
clivity of the ground should never exceed one per¬ 
pendicular to fifteen base. When the ground be¬ 
tween the battery and the enemy is horizontal and 
firm, it will be best to take a position near the ene¬ 
my, as the ricochet shots on such ground do not 
rise much. If the ground is uneven a distant posi¬ 
tion may be more favorable to obtain a grazing fire. 
Positions should be so chosen that hollows, woods, 
villages, &c., on the front, or flank of the line occu¬ 
pied by the troops, may be thoroughly swept, to 
prevent the enemy’s columns from approaching un¬ 
der cover. 

Advantage should be taken of any unevenness of 
ground to place the artillery under cover until called 
into action. But all broken ground occupied by 
batteries should be thoroughly examined, and the 
avenues Jeading to it, by which the enemy’s cavalry 
might fall upon the batteries, should be obstructed. 
Stony ground is a bad position for a battery, owing 
to the effect of the enemy’s shot in scattering the 
stones. Very even ground is unfavorable, as well 
as uneven ground which opens in a funnel shape 
outwards from the battery, as the enemy is enabled 
in either case to concentrate his fire from an ex¬ 
tended front upon the battery. Rough ground 


xxiii 


Dreaks the effects of the enemy’s ricochet shots, and 
when it presents bluffs or perpendicular faces to¬ 
wards the enemy it will stop the balls that strike 
those parts. Undulating ground hinders the enemy 
from observing the effects of his fire. If the ground 
in rear of the battery is hidden the enemy will ge¬ 
nerally aim too high ; but if the battery is relieved 
against the sky it will assist his aim. It must be 
borne in mind that in taking advantage of undula¬ 
tions to cover a battery it will not do to fire from 
behind the covering ridge, as the aim and range 
will be rendered very uncertain. Batteries should 
never be placed directly in front of other troops, 
since they necessarily attract the enemy’s fire to 
them, and would therefore cause great damage to 
the troops in rear. 

V. Management of the fire of batteries. The 
management of the fire with regard to the projectile 
to be used is very important. It has been observed 
that the ball and howitz produce a greater moral 
effect upon troops than grape. When it is taken 
into consideration that a six pdr. shot will take off 
twenty-four ranks at a distance of 500 to 600 yards, 
the tremendous effect of a smashing fire of ball upon 
a column may be readily understood. A fire of ball 
or shells should, therefore, be opened upon troops at 
a distance, when they are in mass, in several lines, 
or when an enemy’s line can be enfiladed. When 
an enemy’s column is advancing a fire of ball 
should be opened on the head of the column; and if 
it be in retreat the aim ought to be directed on the 
centre. The fire of shells is good against cavalry, 
as it produces disorder from the explosion of the 
shell. 

A fire of grape or canister should be opened on 
troops in line, or in open order, but not at distances 


xxiv 


greater than 600 or 800 yards. In an attack upon 
troops in line, a battery may advance to within 400 
or 500 yards before opening its fire of grape; and 
even nearer if the ground is unfavorable to ricochet, 
and there is but little danger from an attack of thd 
enemy’s skirmishers on the flanks of the battery. 
When an enemy’s battery advances nearer than 
point blank range, a fire of grape should be opened 
upon it, just at the moment when having com¬ 
menced the movement to place the pieces in bat¬ 
tery, the flanks of the horses will be offered to the 
fire. 

As a general rule, the aim should be rather low, 
as ricochet shois produce considerable moral effect. 
For this purpose, when the ground is favorable to 
this fire, the aim should be at the mark, but rather 
under it for distances within 1200 yards; beyond 
this, and up to 1800 yards, when this fire becomes 
inefficacious, the piece may be fired with an eleva¬ 
tion of one degree between its axis and the ground. 

Our fire should be concentrated on several points 
in succession ; but the pieces of the battery should 
be separated at wide intervals, when the position 
will admit of it, to offer fewer chances to the diver¬ 
gence of' the enemy’s shot. It is seldom of any use 
to fire a single piece at a small mark, as a group 
of a few individuals ; if it be suspected that any 
important personage may be in such a group we 
should let them have the discharge of an entire 
battery at once. 

The ammunition of the pieces should be econo¬ 
mized, unless it be necessary to drown the fears of 
new troops in noise. 

VI. Position of Batteries in Attacking and De~ 
fending Intrenchments. In the attack of intrenched 
positions, the batteries should be placed to obtain 


enfilading views on the enemy’s lines, and a fire be 
opened with ball and shells from pieces of the hea¬ 
viest calibre. When our column of attack has ar¬ 
rived near the works, the batteries should be so 
posted as to support it if repulsed. 

In the defence of works, the pieces should be so 
placed as to cross their fire upon the ground over 
which the enemy must approach. The heaviest 
pieces should be placed on the most secure points, 
and in such positions that their fire may not incom¬ 
mode the troops defending the work. The light 
guns should be placed at the advanced points, as 
they can be most easily withdrawn. The howitzers 
should occupy points from which hollows, woods, 
&c., in advance of the works, can be reached by 
their shells. 

VII. Effects , <f*c., of Batteries for Harbor Defence. 
As very erroneous and vague notions are at present 
afloat with respect to the effects of artillery against 
shipping and batteries, a statement of some of the 
more settled points may not be here misplaced. 

Heavy ordnance, from 24 pdr. guns upwards, 8 
inch sea-coast howitzers, commonly known as Pair- 
han guns , and heavy mortars, should alone be used 
for harbor defences. 

The projectiles of heavy guns, after ricocheting un¬ 
der angles of 4° or 5° on water, lose but little of their 
velocity ; the ball, for example, of a 24 pdr., after a 
ricochet, preserves sufficient force to pierce the side 
of a line-of-battle ship at 600 or 700 yards distance. 

The destructive ranges of sea-coast howitzers, 
fired with heavy charges, are as high as between 
3000 .and 4000 yards. Those of heavy mortars are 
even greater, and their shells fired under great an¬ 
gles will break through two or three decks of a ship. 
Both of these projectiles produce the most destruc- 


XXVI 


tive effects when they lodge and explode in timber, 
or between decks. \ 

Batteries, if properly placed, have the two-fold 
advantage of striking shipping either by a direct 
aim, or by ricochet; and this does not require, as is 
generally thought, that the battery should be at the 
water’s edge. When shipping cannot approach 
nearer to the battery than between 200 and 300 yards, 
it may be from 50 to 53 feet above the water level 
and still attain a vessel by ricochet shot, by aiming 
rather low. To effect this the aim should be so 
taken that the ball, were it to plunge under the ves¬ 
sel, would pass about as far below the water level 
as the upper deck is above it. If vessels cannot 
get nearer than between 400 and 500 yards, then 
the battery will have the same advantages if placed 
from 80 to 100 feet above the water level. These 
advantages of ricochet double the chances of batte¬ 
ries, during a calm, at distances between 200 and 
700 yards. 

The effect of projectiles upon strong masonry is 
very gradual. It requires several hours of cool, 
systematic firing, at very short ranges, to open a 
useful breach in a well built wall of good stone. 
The effect of shells, fired against walls of brick 
even, is absolutely null, as they invariably break, 
and make but a slight impression upon the wall. A 
brick arch 3 feet thick, covered with about the same 
thickness of earth, will sustain, without injury, the 
shock of the largest shells falling from the greatest 
heights. 

In the fire from shipping upon elevated batteries 
the advantages from ricochet shots are lost. Even 
when the battery is low if the ground between it 
and the water be cut into perpendicular steps, the 
effects of ricochet will be considerably lessened, as 


XXVI1 


every shot that strikes the face of a step will be 
stopped. 

Batteries have this farther advantage over ves¬ 
sels, that the hull and rigging of the latter present 
a large vulnerable mark for every gun of the for¬ 
mer. To compensate for this ships, can bring a 
large number of guns to bear on the same point. 

When batteries are low, and the water will ad¬ 
mit of shipping to approach within musket range, 
the gunners may be driven from their pieces by a 
fire from the ship tops. . To provide against this, 
there should be a few light guns on secure points 
to fire into the tops with grape. 






¥ 


DIRECTIONS TO THE BINDER. 


/ 

Explanations of Plate I. and Plate to follow Page, 12 


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152 






FIELD FORTIFICATION. 


CHAPTER I. 


NOMENCLATURE AND GENERAL PRINCIPLES. 

1. All dispositions made to enable an armed 
force to resist, with advantage, the attack of one 
superior to it in numbers, belong to the Art of 
Fortification. 

2. The means used to strengthen a position, may 
be either those presented by nature, as precipices, 
woods, rivers, &c., or those formed by art, as shel¬ 
ters of earth, stone, wood, &c. 

3. If the artificial obstacles are of a durable cha¬ 
racter, and the position is to be permanently occu¬ 
pied, the works receive the name of Permanent 
Fortification ; but when the position is to be occu¬ 
pied only for a short period, or during the operations 
of a campaign, perishable materials, as earth and 
wood, are mostly used, and the works are denomi¬ 
nated Temporary or Field Fortification. 

4. The general appellation of Intrenchments is 
applied to all field works ; and a position strength¬ 
ened by them, is said to be Intrenched. 

5 . To enable troops to fight with advantage, the 
intrenchments should shelter them from the enemy’s 

l 



2 


\ 

fire; be an obstacle in themselves to the enemy’s 
progress ; and afford the assailed the means of 
using their weapons with effect. To satisfy these 
essential conditions, the component parts of every 
intrenchmont should consist of a covering mass, or 
embankment, denominated the 'parapet, to intercept 
the enemy’s missiles, to enable the assailed to use 
their weapons with effect, and to present an obsta¬ 
cle to the enemy’s progress, and of a ditch, which, 
from its position and proximity to the parapet, sub¬ 
serves the double purpose of increasing the obsta¬ 
cle which the enemy must surmount before reach¬ 
ing the assailed, and of furnishing the earth to form 
the parapet. 

6. Intrenchments should be regarded only as ac¬ 
cessories to the defence of a position. They are 
inert masses, which, consuming a portion of the 
enemy’s efforts, and detaining him in an exposed 
situation to the fire of the assailed, insure his 
defeat. 

7. The general form of a parapet and ditch, to 
fulfil the above conditions, will be best understood 
by an examination of the profile (Fig. 1), which is 
a section of the intrenchment made, by a vertical 
plane, perpendicular to the general direction of the 
intrenchment. 

8. The exterior slope is the part of the parapet 
towards the enemy ; it is usually made with the 
same slope that the earth when first thrown up 
naturally takes. 

The top of the parapet, denominated the superior 
slope, is the line along which the assailed fire on 
the enemy. 

The interior 'slope , sometimes denominated the 
breast height, is the part against which the assailed 
naturally 'ean in the act of firing. 


3 


The banquette is a small terrace on which the sol¬ 
dier stands to deliver his tire ; the top of it is de¬ 
nominated the tread, and the inclined plane by which 
it is ascended the slope. 

The term crest is applied to those points of the 
profile, where a salient angle is formed ; and where 
a re-entering angle is formed by two lines, the term 
foot is applied to the point, in connection with the 
name of the superior line ; thus,ybo£ of the exterior 
slope; foot of the interior slope, dfc. 

The berm is a horizontal space left between the 
parapet and the ditch, to prevent the earth from 
yielding. 

The slope of the ditch next to the parapet is the 
scarp; the opposite side the counterscarp. 

The glacis is a small mound of earth raised in 
front of the ditch; it is seldom used in fieid works, 
and is therefore not a constituent part of their pro¬ 
file. 

8. The profile shows only the outline of an in- 
trenchment in elevation, and by itself is not suffi¬ 
cient to point out the relative bearing of all the 
parts. A plan, or trace, which exhibits the direc¬ 
tion of the different lines of the parapet, &c., is, 
in conjunction with the profile, requisite for this 
purpose. 

9. The plan of intrenchments in general should be 
so arranged as to procure a mutual defence of the 
parts. To effect this, certain parts are thrown for¬ 
ward towards the enemy, to receive his attack; 
they are denominated advanced parts; other por¬ 
tions, denominated retired parts, are withdrawn from 
the enemy, and protect by their fire the advanced 
parts. This arrangement naturally indicates that 
the general outline of the plan must present an an¬ 
gular system ; some of the angular points, denomi 


4 


nated salients, being towards the enemy, and others 
denominated re-enterings, towards the assailed. 

10. When such a disposition is made, it is de¬ 
nominated & flanked disposition; because the ene¬ 
my’s flank is attained by the fire of the retired parts 
when he is advancing upon the salients. 

11. A flanked disposition is shown in Fig. 2. 
The advanced parts are denominated faces ; the re¬ 
tired parts, which protect the faces, the flanks ; the 
retired part connecting the flanks is the curtain. 

An angle formed by two faces is denominated a 
salient angle; that formed by two retired parts a 
re-entering angle; and one made by a face and the 
opposite flank, an angle of defence. 

The line bisecting a salient angle is denominated 
the capital; the distance from a salient to its oppo¬ 
site flank is a line of defence. 

12. The form of a parapet, and the direction in 
which a soldier naturally aims in firing over one, are 
the causes of two of the most important defects of 
intrenchments. Owing to the form of the parape*. 
and its height, the fire can take effect only at some 
distance beyond it, so that when the enemy has ap¬ 
proached very near the parapet, particularly when 
he is in the ditch, the fire will pass over his head, 
unless the flanks are so arranged that their fire will 
sweep every point of the ditch ; an arrangeme it of 
which particular angular systems are alone sus¬ 
ceptible. This space, where the enemy can .ind a 
shelter, is, generally, in the ditches at the re-enter¬ 
ing angles. It is denominated a dead space, or dead 
angle. 

13. In delivering his fire a soldier usually aims 
directly to the front, so that the line of fire and the 
parapet make nearly a right angle with each other. 
In consequence of this the salients receive no pro- 


5 

tection from themselves, and there is an angular 
space in front of each of them (which is equal to 
the supplement of the salient angle) that is defended 
only by the fire of the flanks. This space is deno¬ 
minated a sector without fire. 

The dead angles, therefore, depend partly on the 
flanking dispositions, but chiefly on the height of 
the parapet. The sectors without fire are defects 
of the plan alone. 

14. The attack and defence of intrenchments 
bear a necessary relation to each other; and it is 
upon a knowledge of the course pursued by the 
assailant, that the principles regulating the defence 
should be founded. 

15. An attack is, generally, opened by a fire of 
the enemy’s artillery, whose object is to silence the 
fire of the intrenchments, and to drive the assailed 
from the parapet; when this object is attained, a 
storming party, which usually consists of a detach¬ 
ment of engineer troops, a column of attack, and a 
reserve, is sent forward, under the fire of the artil¬ 
lery, to the assault. The detachment of engineer 
troops precedes the column of attack, and removes 
all obstacles that obstruct its passage into the ditch. 
The line of march is directed upon a salient, through 
a sector without fire, and on the prolongation of the 
capital, as this line is least exposed to the fire of the 
works. 

When the ditch is gained, the party makes its 
way to a re-entering angle, where, sheltered from the 
fire of the flanks, the work is entered by the column 
of attack, either by making a breach in the para¬ 
pet, or else by means of ladders. The reserve 
supports the column of attack in case of need ; 
and, if it is driven from the works, covers its re¬ 
treat. 

16. The manner of making the defence is with 
1 * 


6 


artillery, musketry, the bayonet and sorties. The 
enemy is attained at a distance by the fire of the 
artillery and musketry, whose effect will chiefly de¬ 
pend on the length of time that he is kept exposed 
to it by the ditch, and the obstacles in fiont of it. 
The bayonet is resorted to, as soon as the enemy 
shows himself on the berm; and sorties are made, 
either when any irresolution or confusion is seen in 
the enemy’s ranks, or at the moment he is repulsed 
from the parapet. 

It is from this general outline of the attack and 
defence, that the following principles, which regu¬ 
late the plan and profile of intrenchments, are de¬ 
duced. 


I. 

17. A flanked disposition should he the basis of the 
plan of all inirenchments. 

The flanks sweep with their fire the ground in 
front of the faces ; remove sectors without fire and 
dead angles ; cross their fire in front of the salients ; 
and take the enemy’s column in flank. 

II. 

/ 1 

Every angle of defence should he 90°. 

An acute angle of defence exposes the faces to 
the fire of the flanks ; an obtuse angle leaves a por¬ 
tion of the ground in front of the face undefended. 

IIT. 

A line of defence should not exceed 160 yards. 

A close fire of musketry is more deadly than one 
of artillery; the musket will kill at distances be- 


7 


tween 250 and 300 yards, but its fire is not verj 
cortain beyond 160 yards; moreover, the enemy 
should be attained by the musketry before he gains 
the salients. 

IV. 

A salient angle should not he less than 60°. 

A salient less than 60° is too weak to withstand 
the effects of weather ; the interior space which it 
encloses is too confined for the manoeuvres of the 
troops; it forms a large sector without fire in front 
of it; the faces of acute salients are, from their 
position, more exposed to the enemy’s enfilading 
fire than when the angle is obtuse. 

V. 

A strong profile is essential to a vigorous defence. 

The rapidity with which a column of attack 
approaches, and the short time it remains exposed 
to the fire of the work, unless detained by obstacles 
in front of the ditch, render its loss, generally, so 
trifling as not to check its march, until it arrives at 
the crest of the counterscarp. Here, if the ditch is 
deep, some delay ensues in entering it, during which 
the column is exposed to a warm fire within short 
range. When the ditch is entered, a more serious 
obstacle remains to be encountered, in the additional 
height of the parapet and scarp ; and when this 
obstacle is overcome, the enemy presents himself in 
a fatigued and exhausted state to the bayonets of the 
assailed, who have mounted on the top of their 
parapet to meet and drive him back into the ditch. 


8 




VI. 

77 le bayonet should be chiefly relied on to repel the 

enemy. 

Unless the assailed are determined to meet the 
enemy at the point of the bayonet, they must eva 
cuate their works so soon as he has entered the 
ditch; a longer delay to retreat would be followed 
by the most disastrous consequences. 

The results of innumerable actions prove that 
the defence with the bayonet is the surest method 
of repelling the enemy. The assailed, having now 
become the assailant, are assisted by that moral 
effect which is produced by a change from a defen¬ 
sive to an offensive attitude. They have moreover 
the advantages of position and freshness over a 
climbing and exhausted enemy. 

VII. 

Inlrenchmenls should be arranged to facilitate sorties. 

A sortie made on the flank of the enemy, at the 
moment when his column is either checked by the 
fire of the works, or is in a state of disorder when 
entering the ditch, will generally prove decisive in 
repelling his attack. 

This principle, however, is applicable only to en 
gagements with large bodies of troops, defending 
works open in their rear. A small detachment 
should generally rest satisfied with repulsing the 
attack ; and should not give up the advantages of 
their position, by sallying out to engage the enemy 
on unequal terms. 


VIII. 

Intrenchments should contain a reserve proportioned 
to their importance. 

The troops engaged in the immediate defence of 
the works might be overpowered by reiterated 
assaults of the enemy, unless they are supported by 
a reserve. The duties of the reserve are to charge 
the enemy in any critical moment of disorder, and 
to cover the retreat of the troops if driven from the 
parapet. 

IX. 

Intrenchmenis should be defended to the last extremity. 

The chief object of intrenchments is to enable 
the assailed to meet the enemy with success; by 
first compelling him to approach, under every dis¬ 
advantage of position, and then, when he has been 
cut up by the fire of the works, and is exhausted 
by his efforts to reach the parapet, to assume the 
offensive, and drive him back at the point of the 
bayonet. This object can only be attained by de¬ 
fending the works to the last extremity; and unless 
attained, intrenchments would serve little other 
purpose than to shelter the assailed from the enemy’s 
fire; for the damage received by the enemy from 
the fire of troops who see safety only in retreat, and 
not in a courageous effort to repel the assault, will 
be necessarily trifling. 

This principle leads to the rejection generally of 
advanced works thrown up in front of the principal 
intrenchments ; and to all dispositions of works in 
several lines, where the object is to retreat, succes¬ 
sively, from one to the other. If an advanced work 
is required for the defence of a point, which cannot 
be defended by the principal works, it should be 


10 


supported by a reserve, and its garrison not be suf¬ 
fered to retreat, until it is in danger of being over¬ 
powered : when it should retire under cover of the 
reserve. As to retreating from one line to another, 
one of two things must happen ; either the first line 
must be evacuated, before the enemy enters the 
ditch, in order that the assailed may gain their 
second line in safety; in which case the first line 
will be of little service : or else, if the assailed wait 
until the assault is made on the parapet before re¬ 
treating, the enemy will enter pell-mell with them 
into the second line, which will thus be of no ser¬ 
vice. 

Troops in action cannot enter into the spirit of 
fortification on paper. A retreat carries with it all 
the moral effects of a defeat; it inspires the assail¬ 
ant ; renders the retreating corps timid ; and impairs 
the confidence of the troops of the second line in 
the strength of their own position, when they see 
the first line carried with such ease. Add to this, 
the confusion that must ensue among the best dis¬ 
ciplined troops, under such circumstances, and the 
importance attached to the principle will be fully 
justified. 


CHAPTER II. 


PLAN OF SIMPLE INTRENCHMENTS, OR THE ELE¬ 
MENTS OF LINES. 

18 . The ground occupied by a work is denomi¬ 
nated the site , or plane of site. 

The command is the height of the interior crest 
above the site ; and the relief is the height of the 
same line above the bottom of the ditch. 

19. A fire is said to be direct , slant , or enfilad¬ 
ing, according as its direction is perpendicular to, 
makes an angle of 30° with, or is on the prolonga¬ 
tion of the line at which it is aimed ; when the line 
is taken in the rear the fire is denominated a reverse 
fire; and when a given space is defended by the 
fire from several points crossing over it, the defence 
is denominated a crossfire. 

20. In planning a work the interior crest is re¬ 
garded as the directing line in regulating the di¬ 
mensions of the faces, flanks, &c., because this 
line shows the column of fire for the defence. 
There exists a necessary subordination between the 
plan, relief, and command^f works, which pre¬ 
vents the dimensions of the one being regulated 
independently of the others; but, without entering 
into a close examination of this necessary co-rela¬ 
tion of the parts, it may be stated generally, that 
faces should vary between 30 and 80 yards, flanks 
between 20 and 40 yards, and curtains should not 
be less than twelve times the relief. 

21. A great variety of figures has been used for 
the plan of simple intrenchments. They may all 
be reduced to the following, the Right Line; the 


12 


Redan; the Lunette , or Detached Bastion; the 
Cremailltre , or Indented Line; the Priest-Cap , or 
Swallow- Tail; the Redoubt; the Star Fort; and 
the Bastion Fort. 

22. -The redan (Fig. 3) is a work consisting of 
two faces ; the gorge , or entrance in the rear, being 
open. This work is used to cover a point in its 
rear; such as a bridge, defile, ford, &c. Having 
no flank defences its salient is unprotected, and to 
obtain a fire in the direction of its capital a short 
face, denominated a pan coupe , is sometimes made 
in its salient angle. 

23. The lunette (Fig. 4) consists of two faces 
and two flanks. This work is used for the same 
purposes as the preceding. It has the same de¬ 
fects ; but possesses the advantages of sweeping 
with the fire of its flanks ground which might be 
badly defended by its faces. 

24. The indented line (Fig. 5) serves to convert 
the direct fire of a right line into a flank and cross 
fire, and is therefore frequently substituted for the 
right line. 

25. The priest-cap (Fig. 6) is seldom used as a 
detached work; but is generally combined with the 
right line and the indented line to procure a flank, 
or cross fire, in front of them. 

26. Any enclosed work of a polygonal form, 
without re-entering angles, is denominated a re¬ 
doubt. This work is used to fortify a position 
which can be attacked on all sides; the works 
which have already been described, being unsuit¬ 
able for this purpose, as their gorges are open, 
and therefore require to be supported by troops, or 
works, in their rear; except when they are so 
situated that an attack cannot be made at the 
gorge. 







































































EXPLANATIONS OF PLATE I. 

Fig. 1. This Fig. shows the ordinary form of the Profile of an 
Intrenchment, in soils of which the Natural Slope is 
one perpendicular to one base. 
a b c d e f is the profile of the Parapet. 
g h i k the profile of the Ditch. 
l m n the profile of the Glacis. 
a b is the Banquette Slope. 
b c Tread of the Banquette, 
c d the Interior Slope. 
d n the Superior Slope. 
e f the Exterior Slope. 
f g the Berm. 
g h the Scarp. 

h i the Bottom of the Ditch, 
i k the Counterscarp. 
a the Foot of the Banquette Slope. 

B the Crest of the Banquette, 
c the Foot of the Interior Slope. 
d the Interior Crest. 
e the Exterior Crest. 

F the Foot of the Exterior Slope, 
s the Crest of the Scarp. 

H the Foot of the Scarp, 
i the Foot of the Counterscarp. 

K the Crest of the Counterscarp. 
m the Crest of the Glacis. 
n the Foot of the Glacis. 

Fig. 2. This Fig. shows the general Plan of Intrenchments with 
Flanking arrangements, 
o a b and e f p are the Advanced Parts, 
s c d e are the Retired Parts. 
a o, a b, e f, and f p are the Faces. 
b c and d e are the Flanks, 
c d the Curtain. 

a d and c f the Lines of Defence, 
o a b and e f p are the Salient Angles. 
bcd and c d e the Re-entering Angles. 
a d f and e c f the Angles of Defence, 
b a c and erg the Sectors without Fire. 

% m and n r the Capitals. 

Fig. 3. This Fig. shows the Plan of the Redan. 
a b and c d are the Faces. 
a d is the Gorge, or Gorge Line. 
b c is a Pan Coup6. 

Fig. 4. Shows the Plan of the Lunette. 
b c and c d are the Faces. 
a b and e d the Flanks. 

Fig. 5. Shows the plan of the Cr6maillere, or Indented Line. 

Fig. 6. Shows the plan of the Priest-cap, or Swallow-tail. 

Fig. 7. Shows the plan of the Square Redoubt, with the faces 
at one angle indented, and at the other arranged with 
a pan-coup6. 

Figs. 8, 9, 10 and 11. Show plans of Star Forts for polygons of 
lour, five, six, and eight sides. 


























































13 


The square (Fig. 7) is the most common form 
for a redoubt, on account of the ease with which 
it is constructed, and the advantage it possesses, 
when combined with several others, of protecting 
the spaces between them by a cross fire. 

All redoubts have the same defects. The ditches 
are unprotected, and there is a sector without fire 
in front of each salient. For the purpose of reme¬ 
dying the sector without fire, it has been proposed 
to convert a portion of each face at the salient 
angles, into an indented line, to procure a fire in the 
direction of the capitals. This method is not of 
practical application; and if it could be applied 
would only serve the purpose of changing the po¬ 
sition of the sectors without fire from the salients 
to other points. 

27. The star fort takes its name from the form of 
the polygonal figure of its plan. (Figs. 8, 9, 10, 
11.) It is an enclosed work, with salient and re¬ 
entering angles; the object of this arrangement 
being to remedy the defects observed in redoubts. 
This, however, is only partially effected in the star 
fort: for, if the polygon is a regular figure, it will 
be found, that, except in the case of a fort with 
eight salients, the fire of the faces does not protect 
the salients ; and that in all cases there are dead 
angles at all the re-enterings. The star fort has, 
moreover, the essential defect, that occupying the 
same space as a redoubt, its interior capacity will 
be much less, and the length of its interior crest 
much greater, than in the redoubt: it will, there¬ 
fore, require more men than the redoubt for its de¬ 
fence, whilst the interior space required for their 
accommodation is diminished. These defects, to¬ 
gether with the time and labor required to throw 
up such a work, have led engineers to proscribe it, 


14 


except in cases where they are compelled by the 
nature of the site to resort to it. 

To plan a star fort, its salients should not be 
less than 60°, and its faces may vary from 30 to 60 
yards. 

28. The bastion fort satisfies more fully the con¬ 
ditions of a good defence, than any other work ; but, 
owing to the time and labor required for its con¬ 
struction, it should be applied only to sites of great 
importance, which demand the presence of troops 
during the operations of a campaign. 

The bastion of a fort may consist of a polygon 
of any number of sides; but for field forts, the 
square and pentagon are generally preferred, owing 
to the labor and construction. To plan a work of 
this kind, a square or pentagon (Fig. 12) is laid out, 
and the sides bisected by perpendiculars ; a distance 
of one eighth of the side is set off on the perpen¬ 
diculars in the square, or one seventh in the penta¬ 
gon ; from the angular points of the polygon, lines 
are drawn through the points thus set off; these 
lines give the direction of the lines of defence; 
from the salients of the polygon distances, equal to 
two sevenths of the side, are set off on the direc¬ 
tion of the line of defence, which give the faces ; 
from the extremity of the faces, the flanks are 
drawn perpendicular to the lines of defence ; the 
extremities of the flanks are connected by the cur¬ 
tains. 

The side of the polygon is termed the exterior 
side; the line bisecting it, the perpendicular; the 
angle at the salient is the flanked angle; the one 
formed by a face and flank, the shoulder angle; the 
one between the flank and curtain, the angle of the 
curtain ; the portion of the work included between 
the capitals of two adjacent bastions is denominated 
a bastioned front , or simply & front. 


15 


An examination of the arrangement of a bas- 
tioned front will show that there are neither dead 
angles nor sectors without fire ; that the salients, 
and all the ground within the range of musketry, 
are protected by formidable columns of direct, flank, 
and cross fire. There is one point in this system 
that demands particular attention, which is, that the 
counterscarp of the ditch, if laid out parallel to the 
interior crest, would form a dead angle along each 
face near the shoulder; because the fire of the flank 
would be intercepted by the crest of the counterscarp. 
To prevent this, either the counterscarps of the faces 
must be prolonged to intersect, and all earth between 
them and the scarp of the flanks and curtain be 
excavated (Fig. 13), or the ditch of each face must 
be inclined up in a slope from the bottom, opposite 
the shoulder (Fig. 14), so that it can be swept by 
the fire of the flank. 

The first method is the best, but requires most 
labor; the second is chiefly objectionable as it gives 
an easy access to the ditch, which might be taken 
advantage of in an assault. It is proposed, to ob¬ 
viate this, to dig a second ditch at the foot of the 
slope across the main ditch, twelve feet wide, and 
about six feet deep ; to make it pointed at the bot¬ 
tom, and to plant a row of palisades in it. The 
profile through the flank (Fig. 14) shows this ar¬ 
rangement. 

Forts have been proposed with half bastions, but, 
being very little superior to the redoubt, and much • 
more difficult of construction, they ought never to 
be used. 

The exterior sides of the bastion fort should not 
exceed 250 yards, nor be less than 125 yards, other¬ 
wise the flanking arrangements will be imperfect. 
With a relief of 24 feet, which is the greatest that, 


16 


in most cases, can be given to field works, and an 
exterior side of 250 yards, the ditch of the curtain 
will be perfectly swept by the fire of the flanks, the 
lines of defence will be nearly 180 yards, a length 
which' admits of a good defence, and the flanks 
will be nearly 30 yards. With a relief of 14 feet, 
the least that will present a tolerable obstacle to an 
assault, and an exterior side of 125 yards, the ditch 
of the curtain will be well flanked, the flanks will 
be nearly 20 yards in length, and the faces between 
30 and 40 yards. Between these limits, the dimen¬ 
sions of the exterior side must vary with the relief. 

29. The defence of enclosed works demands that 
every point of the parapet should be guarded, at the 
moment of assault, either by cannon or musketry. 
The troops may be drawn up for the defence either 
in one, two, or three ranks; and there should, more¬ 
over, be a reserve proportioned to the importance 
attached to the work. The free interior space, de¬ 
nominated the lerre-parade plein , should be suffi¬ 
ciently great to lodge the troops, with the cannon 
and its accessories, and will therefore depend on the 
nature of the defence. The following data will 
suffice to regulate this point. 

Each man will occupy one yard, linear measure, 
along the interior crest, and each cannon from five 
to six yards. The space requisite to lodge each 
man is one and a half square yards ; and about sixty 
square yards should be allowed for each gun. Be¬ 
sides this space an allowance must be made for the 
traverses , which are mounds of earth thrown up in 
the work to cover an outlet, to screen the troops 
from a reverse, or an enfilading fire, &c.; and for 
powder magazines, when they are not placed in the 
traverses. The area occupied by a traverse will 
depend on its dimensions, and cannot be fixed be- 


\ 


17 


forehand; that allowed for a magazine for three or 
four cannon may be estimated at fifteen or twenty 
square yards. 

30. As a field fort must rely entirely on its own 
strength, it should be constructed with such care 
that the enemy will be forced to abandon an attempt 
to storm it, and be obliged to resort to the method 
of regular approaches used in the attack of perma¬ 
nent works. To effect this, all the ground around 
the fort, within the range of cannon, should offer 
no shelter to the enemy from its fire; the ditches 
should be flanked throughout; and the relief be so 
great as to preclude any attempt at scaling the 
work. 



CHAPTER III. 


'discussion of the general profile. 

31. The general form of the parapet is the same 
for all works. Its dimensions will vary with the 
kind of soil used in its construction ; with the time 
and means that can be employed; with the time 
that the work is to remain occupied; and, finally, 
with the time and means that the enemy can dis¬ 
pose of in the attack, and the degree of resistance 
that the work should offer. 

32. The command of the interior crest (Fig. 1.) 
should be regulated so as to intercept the enemy’s 
missiles, ana to shelter the assailed. Men of the 
greatest ordinary stature, in bringing their muskets 
to an aim, do not fire at a higher level than about 
five feet; therefore any mass of this height in front 
of them will just intercept their fire ; but this mass 
would not shelter a man standing behind it; to effect 
this, in the case of the tallest men usually found iij 
the ranks, the interior crest should be at least six 
feet six inches above the terre-parade-plein. The 
command must then be regulated by these two 
facts, and this principle may be laid down. The 
command of a field work over the ground occupied by 
the enemy must never be less than five feet; nor less 
than six feel six inches over that occupied by the as¬ 
sailed. 

But this minimum command would give the as¬ 
sailed only a slight advantage, as the men, when on 
the banquette, would be still much exposed; and 
in an assault the height of the parapet would pre¬ 
sent an inconsiderable obstacle. These defects of 


19 


low works have led engineers to adopt eight feet 
the least height of parapet which will admit of 
respectable defence. The greatest height has been 
fixed at twelve feet, owing to the difficulty of throw¬ 
ing up a work with the ordinary means at hand, 
which are usually only the pick and shovel. 

The thickness of the parapet, which is always 
estimated by the horizontal distance between the 
interior and exterior crests, is regulated by the ma¬ 
terial used for the parapet; the kind of attack, and 
its probable duration. 

PENETRATION INTO WELL-RAMMKD EARTH COMPOSED OF HALF 
SAND AND HALF CLAY. 


18 pounder, 

. 110 yards 



6 feet 6 in. 

18 

ii 

440 

U 



5 

ii 

6 “ 

18 

(4 

880 

U 



4 

ii 

6 “ 

9 

ii 

110 

ii 



4 

ii 

4 “ 

9 

U 

440 

ii 



3 

ii 

4 « 

9 

a 

880 

ii 

\ 



2 

ii 

8 “ 

6 inch howitzer, 

110 

“ charge 3-3 lbs. 4 

ii 

0 “ 

6 

ii ii 

440 

ii 

ii 

ii 

3 

ii 

0 “ 

6 

ii ll 

880 

ii 

ii 

ii 

2 

ii 

0 “ 

24 pounder “ 

110 

ii 

ii 

2-2 lbs. 3 

H 

5 “ 

24 

ii 

440 

ii 

ii 

ii 

2 

ii 

5 “ 

24 

ii 

880 

ii 

ii 

ii 

1 

ii 

6 “ 


The penetrations in f o sand mixed with gravel were about 0 6 
of the above ; into earth mixed with sand and gravel, about 0-9; 
into compact soil of clay, sand and mould, IT ; into common 
soil, loosely thrown up, about twice the above. 


PENETRATION OF MUSKET BALLS. 

inches 


Charge 154 grains, at 34 yards, in oak, 



3 


U <« 44 

<4 44 44 

44 44 44 


134 “ 

154 “ 


a a 

a a 


110 

220 

50 

30 

60 

110 

220 

24 

40 


‘ rammed earth, of clay & sand, 10 

4 44 44 44 44 Q£ 

4 44 44 44 44 gj 

4 44 44 44 (4 g 


bundle of fascines, . . 24 

packed wool of matrasses, 40 















20 


In order to insure perfect security, the thickness of parapets 
ought to be one-half greater than the depth of penetration fur 
nished by experiment. 

As a general rule, the following dimensions may be taken for 
the parapets and other coverings for field-works :— 


Brick wall of one brick, 

Stone ditto, 6 inches, 

White Pine fence, 12 inches 
Yellow ditto, 9 “ 

Oak (seasoned), 4 “ 

Earth, three to four feet, 

Earthen parapet against field-pieces, from 9 to 12 feet. 


Alusket proof. 


From experiments carefully made to ascertain the distance 
into which shot will penetrate the media in most common use 
for forming parapets, the following results have been obtained : 


PENETRATION INTO ROUGH GOOD LIMESTONE MASONRY, WITH A 
CHARGE ONE-THIRD THE WEIGHT OF THE BALL. 


18 pounder shot at about 30 yards, 


18 

ii 

it 

“ 110 

it 



1 

it 

8 

18 

it 

u 

“ 330 

ii 



1 

n 

4 

18 

U 

it 

“ 6G0 

ii 



1 

ii 

0 

9 

it 

n 

“ 30 

it 



1 

ii 

4 

9 

ii 

u 

“ 100 

ii 



1 

ii 

3 

9 

ii 

it 

“ 330 

a 



1 

ii 

0 

9 

u 

it 

“ 660 

u 



0 

ii 

7 


1 foot 9 inches. 


By adding three-fourths of the above distances to themselves, 
the penetration into good brick masonry will be obtained. 

The effect of shells fired against masonry is Very trifling; they 
either break without exploding, or produce but a slight impres¬ 
sion when they explode in contact with the masonry. 


PENETRATION INTO OAK WOOD WITH SAME CHARGE. 

18 pounder shot, at about 440 yards, . . . 3 ft. 0 in. 


18 “ “ “ 

880 

ii 

2 “ 0 “ 

9 ii ii ii 

440 

ii 

2 “ 0 “ 

9 ii ii ii 

880 

ii 

1 “ 0 “ 

6 inch howitzer, “ 

440 

ii 

charge 3-3 lbs. 1 “ 8 “ 

^ ii ii ii 

880 

ii 

“ “ 1 “ 0 “ 

24 pounder howitzer, “ 

440 

ii 

“ 2-2 lbs. 1 “ 3 “ 

04 ii ti ii 

880 

ii 

“ “ 8 “ 0 “ 


The penetration into white pine is about three-fourths greater 
than into oak. 





















21 


34. The superior slope is arranged to defend the 
crest of the counterscarp; to effect which the fire 
should not strike below the crest, nor pass more 
than three feet over it; otherwise, either the coun¬ 
terscarp would be damaged, or the assailed by stoop¬ 
ing when near the crest would find a shelter. The 
inclination of the superior slope, however, should 
not be greater than one-fourth, nor less than one- 
sixth, that is, the base of the slope should be be¬ 
tween four and six times the height. If greater 
than one-fourth, it would make the portion of the 
parapet, about the interior crest, too weak ; and if 
less than one-sixth, the ground directly in front of 
the work would not be so well defended ; more¬ 
over, as artillery cannot be fired at a greater de¬ 
pression than one-sixth, without injuring the car¬ 
riage, this inclination of the superior slope serves 
as a check in rapid firing. 

If, owing to the command, the fire should pass 
higher than three feet above the crest of the coun¬ 
terscarp, it would then be necessary to construct a 
glacis in front of the ditch. It must be so arranged 
that it can be swept by the fire of the work, and be 
commanded by it at least five feet. 

35. The exterior slope is the same that the earth 
naturally assumes. Any means used to make it 
steeper would be injurious ; because they would be 
soon destroyed by the enemy’s fire, and the earth 
giving way, the necessary thickness of the parapet 
would be diminished. 

36. The interior slope receives a base equal to 
one-third its height. This is a result of experience, 
which has shown that it is the most convenient for 
the soldier in leaning forward to deliver his fire over 
a parapet. 

37. The tread of the banquette is placed four feet 


22 


three inches below the interior crest; this will ad« 
mit men of the lowest ordinary stature, to fire con¬ 
veniently over the parapet. Its width is two feet 
for a defence with one rank ; and four feet for two 
or three ranks; because the third rank does not 
fire, and is therefore placed on the banquette slope, 
the base of which is twice the altitude, to render 
the ascent convenient. When the tread of the ban¬ 
quette is very high, and particularly in enclosed 
works, where interior space is wanted, steps may be 
substituted for a slope; the rise of the step should 
be nine inches, and its breadth twelve inches. The 
tread of the banquette should receive a slope of two 
inches to the rear to drain off the surface water. 

38. The berm is a defect in field works, because 
it yields the enemy a foot-hold to breathe a moment, 
before attempting to ascend the exterior slope. It 
is useful in the construction of the work for the 
workmen to stand on; and it throws the weight of 
the parapet back from the scarp, which might be 
crushed out by this pressure. In firm soils, the 
berm may be only from eighteen inches to two feet 
wide ; in other cases, as in marshy soils, it may re¬ 
quire a width of six feet. In all cases, it should be 
six feet below the exterior crest; to prevent the en¬ 
emy, should he form on it, from firing on the troops 
on the banquette. 

39. The ditch should be regulated to furnish the 
earth for the parapet. To determine its dimensions, 
the following points require attention; its depth 
should not be less than six feet, and its width less 
than twenty feet, to present a respectable obstacle 
to the enemy. It cannot, with convenience, be 
made deeper than twelve feet; and its greatest 
width is regulated by the inclination of the superior 


/ 


23 


slope, which, produced, should not pass below the 
crest of the counterscarp. 

40. The slopes of the scarp and counterscarp 
will depend on the nature of the soil, and the action 
on it of frost and rain. The scarp is less steep than 
the counterscarp ; because it has to sustain the 
weight of the parapet. It is usual to give the slope 
of the scarp, a base equal to two-thirds of the base 
of the natural slope of a mound of fresh earth whose 
altitude is equal to the depth of the ditch; the base 
of the counterscarp slope is made equal to one half 
the same base. 

41. To determine the exact dimensions of the 
ditch, for a given parapet, requires a mathematical 
calculation, which will be given in a Note. On 
the field a result may be obtained, approximating 
sufficiently near the truth for practice, by assuming 
the depth of the ditch and dividing the surface of 
the profile of the parapet by it to obtain the width. 
In excavating the ditch it will be found that more 
earth will be furnished at the salients than is 
required there for the parapet; and that the re¬ 
enterings will not always furnish enough. On this 
account, the width of the ditch should not be uniform, 
Dut narrower at the salients than the re-enterings. 


CHAPTER IV. 


MANNER OF REGULATING THE RELIEF OF ENTRENCH¬ 
MENTS ON IRREGULAR SITES. 

42. When a work is placed on level ground, it 
usually receives a uniform relief; but when the 
site is irregular, or there are commanding eminences 
within cannon range, a uniformity of relief cannot 
be preserved, because it might expose the interior 
of the work to the enemy’s view, from the com¬ 
manding points. 

43. The plan will also be modified by the same 
causes. The principal faces should so be placed as 
not only to guard all the points where an enemy 
might approach ; but the enemy should not be able 
to take up their prolongations to obtain an enfilad¬ 
ing, or a reverse fire upon them. The position of 
the points to be guarded, and that of the command¬ 
ing eminences, require to be carefully studied, before 
adopting any definitive plan. The only general 
rules that can be laid down, are to lay out the 
principal lines so as to obtain a direct and cross 
fire, on the approaches of the enemy; and placing 
them, at the same time, as nearly parallel as 
practicable, to the general direction of the crests of 
the commanding heights, in order that the enemy 
occupying the crest may have a direct fire alone on 
these parts. 

44. When the enemy occupies a position more 
elevated than the work, he is said to have a plung¬ 
ing fire on it; and when the relief of the work is so 
regulated as to intercept this fire, the work is said 
to be defiled. 

45. The defilement of field works is not indis* 




25 

pensable to a good defence; nor is it generally 
practicable. It is, however, not only a conservative 
means, but it also inspires the assailed with con¬ 
fidence ; for the soldier regards with distrust the 
strength of his position, when he finds himself 
exposed to the view of the enemy from an elevated 
point. 

44. The defilement of a work is a practical 
operation performed on the ground in the following 
manner:— 

Let abode (Fig. 15) be the plan of a work, 
a lunette for example ; and the points o, o, &c., the 
most elevated points of a commanding position in 
front of the work. At the points a, b, &c., let 
straight poles be planted vertically, and on the poles 
along the gorge line let a point be marked, at three 
feet above the ground. Let two pickets be driven 
in the ground along the gorge line, and a cord a , b , 
or a straight edge of pine, be fastened to them, on 
the same level as the two points marked on the 
poles at a and e. Let an observer now place him¬ 
self in the rear of a b , so as to bring the poles at 

b, c, and d, and the points o, o, &c., within the 
same field of vision. Let observers be placed at b, 

c, and d. The first observer now sights along a b, 
until he brings his eye in the position that a b will 
appear tangent to the most elevated of the points o. 
Having accurately determined this position, he next 
directs the other observers to slide their hands along 
the poles until they are brought into the same plane 
of vision with the point o, and the line a b, and to 
mark those points on the poles. These points, to¬ 
gether with the two first marked, will evident 1 / be 
in the same plane, and this plane, produced, will be 
tangent to the highest point o. It is denominated 
the Rampant Plane. Now if a point be marked on 

3 


1*6 

each pole, at five feet above the points thus deter¬ 
mined, these points will be contained in a second 
ideal plane, parallel to the first, and five feet above 
it. This plane is denominated the Plane of Defile¬ 
ment, and the interior crests of the work are con¬ 
tained in this plane, being the lines joining the 
highest points marked on the poles. 

As the gorge line is farthest from the heights, and 
the rampant plane ascends towards them, it will ne¬ 
cessarily pass at more than three feet above every 
other point of the parade of the work; and the 
plane of defilement, in like manner, will pass at 
eight feet above the parade at the gorge, and at five 
feet above the highest point o. A plane of defile¬ 
ment is therefore defined to be, that plane which, 
containing the interior crests of a work, passes at 
least eight feet above every point of the parade, and 
at least five feet above every point that the enemy can 
occupy within the range of cannon, which range may 
be taken, with safety, at one thousand yards. 

45. When a work is placed in a hollow formed 
by two eminences, and is exposed to both a direct 
and reverse fire from them, it cannot be defiled by 
the means just explained, without giving it a relief 
generally too great for field w r orks. To avoid this 
the method of reverse defilement must be resorted 
to. 

46. Let abode (Fig. 16) be the plan of a lu¬ 
nette, placed between the two eminences o, o'; its 
face and flank a b c being exposed to the direct fire 
from o, and a reverse fire from o'; the other face 
and flank being in like manner exposed to a direct 
and a reverse fire. 

47. Suppose a section of the work (Fig. 17) to 
be made by a vertical plane, passing through the 
highest points o and o'. If in this plane a vertical, 


27 


a b, be drawn, corresponding- to the capital of the 
work, and eight feet be set off on this vertical from 
the point a, and two verticals be drawn through the 
points o and o', and five feet be set off on each of 
them; and then the points c and c’ be joined with 
d, it is obvious that the interior crest of the parapet 
a, being placed on the line c d, will screen all the 
ground in the rear of it, as far as the capital, from 
the direct fire from o. The parapet b being regu¬ 
lated in a similar manner, will screen all the ground 
behind it as far as the same line. But the fire from 
o' would take the parapet a in reverse, and that 
from o the parapet b ; to prevent this, a covering 
mass, denominated a traverse, must be erected on 
the line of the capital, and a sufficient height be 
given to it to screen both a and b from a reverse 
fire. To effect this, let eighteen inches be set off' 
above the interior crests of a and b ; the point e 
being joined with c', and the point e' with c; it is 
here also obvious, that if the top of the traverse be 
placed on the line c e', it will effectually screen both 
the parapets from all reverse fire; because every 
shot that strikes the top of it will pass at least 
eighteen inches above the two parapets, and, since 
the banquettes are four feet three inches below the 
interior crests, the shot must pass five feet nine 
inches above the banquettes, which will be quite 
sufficient to clear the heads of the men when on the 
banquettes. This illustration explains the spirit of 
the method of reverse defilement. The operation 
itself is performed in the following manner. 

48. Poles (Fig. 16) are planted at the points 
a e c, Sic., and one at the point f, where the lines 
of the capital and gorge intersect. On the pole 
f, a point is marked three feet above the ground, 
and a point is likewise marked on the pole at c, 


28 


which should be one foot six inches higher than 
that on f ; that is, if the ground between the two 
poles be level, the point on c will be four feet six 
inches above the ground. Two stout pickets may 
next be planted between f and c, and a cord, or 
a straight edge, be fastened to them, so as to be 
in the same line as the points marked on the 
poles. 

Observers are then placed at the poles a and b ; 
and another places himself behind the cord so as to 
bring the posts o, a, and b, in the field of vision 
with it; then shifting the position of the eye until 
the cord is brought tangent to the highest point on 
o, he directs the observers at a and b, to mark on 
the respective poles the points where the plane of 
vision intersects them. This operation will de¬ 
termine the rampant plane for one half the work 
a b c f, that for the other half will be determined 
by a similar process. If then a distance of five 
feet be set off on each pole above the points thus 
determined, these points will fix the position of the 
interior crests. 

It is obvious that the interior crest of the part 
a b c is not in the same plane as that of the part 
c d e. These two planes are denominated ■planes 

of direct defilement. 

49. To determine the height of the traverse is 
the next step. To do this, the height of the tread 
of the banquette is ascertained on the three poles, 
b, c, d, and a distance of nine inches is set off on 
each pole above the tread. Between the points 
thus determined a cord is stretched, or if the 
distance be too great for this, two pickets may 
be placed between b and c, and a cord, or straight 
edge, be fastened to them in the required direction. 
An observer is then placed, at the pole f, and 


29 


another places himself behind the line b c, so as to 
bring the cord, and the points o' and f, in the field 
of vision; he then shifts the position of the eye 
until the cord is brought to touch the point o' ; he 
then directs the observer at f to mark the point 
on the pole where it is intersected by the plane of 
vision. A similar operation is performed with 
the point o, and the face c d, and above the highest 
point thus determined on f, a distance of five feet 
is set off for the top of the traverse at f ; and five 
feet nine inches is set off above the tread of the 
banquette at c for the top of the traverse at that 
point. 

The planes which determine the top of the 
traverse, are termed planes of reverse defilement. 

50. The traverse is finished on top like the roof 
of a house, with a slight pitch ; its thickness at top 
should seldom exceed ten feet, and will be regulated 
by the means the enemy can bring to the attack; 
its sides are made with the natural slope of the 
earth ; but, when the height of the traverse is con¬ 
siderable, the base of the side slopes would occupy 
a large portion of the interior space ; to remedy 
this, in some measure, the portion of the sides 
which are below the planes of direct defilement, 
may be made steeper than the natural slope ; the 
earth being retained by a facing of sods, &c. 

51. When the salient of the work is arranged for 
defence, the traverse cannot be extended to the 
salient angle; it is usual to change its direction 
within some yards of the salient, and unite it with 
the face most exposed. Traverses are also used to 
cover faces exposed to an enfilade fire ; for this pur¬ 
pose they are placed perpendicular to the face to be 
covered. If several are required, they may be 
placed twenty or thirty yards apart; each traverse 

3* 


should be about twenty-four feet long, and thick 
enough to be cannon proof. 

52. The cases of defilement here examined, are 
those of works open at the gorge; the same princi¬ 
ples, and similar methods, would be applied to en¬ 
closed works. After the plan of the work has been 
regulated, the arrangement of the traverses next 
demands the attention; the only rule that can be 
laid down is, to place them in the most favorable 
position to intercept the reverse and enfilading fire 
of the enemy ; and if there should be a choice with 
respect to several positions, to select the one which 
will give the lowest traverse. 

53. The difficulty of defilement, owing to the 
great relief that may be required for the parapets, 
the labor of erecting the traverses, and the room 
which they occupy within the work, which is fre¬ 
quently wanted for the defence, restricts its appli¬ 
cation mostly to enclosed works, which are to re¬ 
main occupied during some time, and whose 
position, from some point to be defended, cannot be 
shifted. 

54. If it is not even probable that a commanding 
eminence will be occupied by the enemy, neverthe¬ 
less should the defence be not impaired, it will be 
better to place the work beyond the cannon range 
of the eminence. 

55. The irregularity in the profile of the parapet, 
caused by defilement, will occasion a correspondent 
irregularity in that of the ditch. Where the para¬ 
pet is highest, the ditch will require to be widest 
and deepest; for, in order to avoid the removal of 
the earth to considerable distances, it is best that 
the earth for each portion of the parapet should be 
taken from the ditch in front of it. No other rule 
can be laid down in this case, than to keep the di- 


oi 

mensions of the ditch within the prescribed limits ; 
and, if this will not admit of its counterscarp being 
well defended, to raise a glacis in front of it, subject 
to the fire of the work. 


CHAPTER V. 


MANNER OF THROWING UP A WORK. 

56. The foregoing chapters contain all that is 
requisite to determine the plan and relief of field 
works under all circumstances of variety of ground. 
To follow a natural order, the next steps will be to 
describe the manner of laying the work out on the 
field, which is termed profiling ; the distribution of 
the workmen to excavate the ditch, and form the 
parapet; and the precautions to be observed in the 
construction. 

57. Poles (Fig. 18) having been planted at the 
angles of the work, and the height of the interior 
crest marked on them, a line is traced on the ground, 
with a pick, showing the direction of the interior 
crests. At suitable distances, say from twenty to 
thirty yards apart, cords are stretched between two 
stout pickets, in a direction perpendicular to the 
line marked out by the pick ; these cords should be 
exactly horizontal. A stout square picket is driven 
firmly into the ground, where the cord crosses 
above the pick-line, and a slip of pine, on which 
the height of the interior crest is marked, is nailed 
to the picket. The thickness of the parapet is 
measured on the cord, and a picket driven into the 
ground to mark the point. The base of the inte¬ 
rior slope, and the tread of the banquette, are set 
off in a similar manner; and a slip of deal is nailed 
to each of the pickets. The height of the interior 
crest, and the tread of the banquette, are easily 
ascertained, from the position of the cord, and the 




EXPLANATIONS OF PLATE II. 

Fig. 12. Shows the plan of a Bastioned Fort, constructed on a 
Square. 

a. b is the Exterior Side 
c d the Perpendicular. 
a. the Salient Angle. 
e the Shoulder Antrle. 
h the Angle of the Curtain. 

Note. —The nomenclature of the other parts is the 
same as in Fig. 2. 

Fig. 13. Shows the plan of a Bastioned Front, with the entire 
ditch excavated in front of the curtain c. 

Fig. 14. Shows the same with the ditches of the faces pro¬ 
longed upwards to c in a slope. This arrangement 
will be best understood from the Section Fig. 14. 

Fig. 15. a b c d e is the position of the interior crest marked 
out on the ground ; a e is a cord or straight edge, 
placed along the gorge line a e, three feet above the 
ground; o, o' are the commanding eminences. 

Fig. 16. f c is the position of the capital, with a cord sketched 
between the poles at f c; the other lines same as 
Figure 15. 

Fig. 17. a and b are the profiles of the parapets ; c that of the 
traverse ; o, o' the commanding eminences; cd, c 1 d' 
the lines of direct fire ; c e and c' e' the lines of re¬ 
verse fire. * 

Fig 18. Shows a profile made of slips of pine, or of cord. 




11 £ 1 j 


lid l!5 


l id! I 


PnJ.:. . - - 




























































































33 


interior crest; these points having been marked on 
their respective slips, the outline of the parapet is 
shown by connecting them by other slips, which 
are nailed to the uprights ; the banquette slope, and 
exterior slope, will be determined by a similar 
process. 

58. From the profi.es thus formed perpendicular 
to the interior crests, the oblique profiles at the 
angles can readily be set up, by a process which 
will suggest itself without explanation. 

59. Having completed the profiling, the foot of 
the banquette, and that of the exterior slope, are 
marked out with the pick, and also the crests of the 
scarp and counterscarp. All the arrangements pre¬ 
paratory to commencing the excavation are now 
complete. 

60. Experience has shown that, in ordinary soils, 
a man with a pick can furnish employment to two 
men with shovels; that, not to be in each other’s 
way, the men should be from four-and-a-half to six 
feet apart; and, finally, that a shovel full of earth 
can be pitched by a man twelve feet in a horizontal 
direction, or six feet in a vertical direction. 

61. To distribute the workmen, the counterscarp 
crest is divided off into lengths of twelve feet, and 
the interior crest into lengths of nine feet. These 
points might be marked out by pickets numbered 
one, two, three, &c. In each area, thus marked out, 
a working party is arranged consisting of a pick 
with two shovels placed near the counterscarp, two 
shovels near the scarp, and one man to spread, and 
one to ram the earth, for two working parties. 

62. The pick commences by breaking ground so 
far from the counterscarp crest (Fig. 19) that, by 
digging vertically three feet, he will arrive at the 
position of the counterscarp. The excavation is 


34 


carried on at the same depth of three feet, advancing 
towards the scarp, where the same precaution is 
observed as at the counterscarp. The earth is 
thrown forward, and evenly spread and rammed, in 
'layers of about twelve inches, from the banquette 
slope to the exterior slope. 

63. For the facility of entering the ditch, whilst 
working, the offsets, at the scarp and counterscarp, 
may be formed into steps with a rise of eighteen 
inches each ; and, if the ditch is deeper than six 
feet, an offset, about four feet broad, should be left 
at the scarp, about mid-depth of the ditch, to place 
a relay of shovels to throw the earth on the berm. 
In some cases, a scaffold of plank is raised in the 
ditch for the same purpose. 

64. When the ditch has been excavated to the 
bottom, the offsets are cut away, and the proper 
slopes given to the sides. The earth furnished by 
the offsets, if not required to complete the parapet, 
may be formed into a small glacis. 

65. If the soil is stony, the vegetable mould on 
the surface should be scraped off, and reserved to 
form the top of the parapet, which should be made 
of earth of this kind, to the depth of at least eight¬ 
een inches, to prevent injury to the troops from the 
effect of a shot striking the top, and scattering the 
pebbles in their faces. 

66. In making the parapet, care should be taken 
to form a drain, at some suitable point, to carry off 
the water from the interior into the ditch. The 
water from the drain should not be suffered to run 
down the scarp, as it would soon destroy it. A 
gutter, formed of boards, should be made to prevent 
this. 

67. The time required to throw up a work will 
depend on the nature of the soil and the expertness 


35 


of the laborers. From troops unaccustomed to the 
use of ditching tools, six cubic yards may be con¬ 
sidered a fair day’s work in ordinary soils, when the 
earth is not thrown higher than six feet; but when 
a relay is placed on an offset in the ditch, from four 
to five cubic yards may be taken as the result of a 
day’s work for each man. Expert workmen will 
throw up from eight to ten cubic yards at task¬ 
work. 


I 


CHAPTER VI. 


REVETMENTS. 

68. A revetment consists of a facing of stone, 
wood, sods, or any other material, to sustain an 
embankment, when it receives a slope steeper than 
the natural slope. 

69. In field works revetments are used only for 
the interior slope of the parapet and for the scarp ; 
for the first sods, pisa, fascines, hurdles, gabions 
and plank, are chiefly used ; and for the last, timber. 

70. Revetment of sods. Sod work forms a strong 
and durable revetment. The sods should be cut 
from a well-clothed sward, with the grass of a fine 
short blade, and thickly matted roots. If the grass 
is long, it should be mowed before the sod is cut. 

Sods are of two sizes (Fig. 20), one termed 
stretchers , are twelve inches square, and four-and- 
a-half inches thick ; the others, termed headers , are 
eighteen inches long, twelve inches broad, and four- 
and-a-half inches thick. 

71. The sod revetment (Fig. 21) is commenced 
as soon as the parapet is raised to the level of the 
tread of the banquette. A course of sods is then 
aid, either horizontal or a little inclined from the 
banquette; the course consists of two stretchers and 
one header alternating, the end of the header laid to 
the front. The grass side is laid downward; and 
the sods should protrude a little beyond the line of 
the interior slope, for the purpose of trimming the 
course even at top, before laying another, and to 
make the interior slope regular. The course is 


37 


firmly settled, by tapping each sod as it is laid with 
a spade or a wooden mallet; and the earth of the 
parapet is packed closely behind the course. 

A second course is laid on the first, so as to cover 
the joints, or, as it is termed, to break, joints with it; 
using otherwise the same precautions as with the 
first. The top course is laid with the grass up; 
and in some cases pegs are driven through the 
sods of two courses to connect the whole more 
firmly, which is, however, by no means necessary to 
form a strong sodding. 

72. When cut from a wet soil, the sods should 
not be lain until they are partially dried otherwise 
they will shrink, and the revetment will crack in 
drying. In hot weather the revetment should be 
watered frequently, until the grass puts forth. 
The sods are cut rather larger than required for 
use ; and are trimmed to a proper size from a model 
sod. 

73. Pisa revetment. Ordinary earth, if mixed 
with a proper proportion of clay, and the whole well 
kneaded with just water enough to cause the parti¬ 
cles to adhere when squeezed in the hand, may be 
used for a revetment, and is termed a pisa revet¬ 
ment. Sometimes chopped straw is mixed up with 
the mass to cause it to bind better. 

74. The pisa is laid in layers of twelve inches 
thick, and two feet broad, and well packed. The 
same precautions should be taken in forming the 
parapet behind it as in sod revetments. The face 
of the revetment may be sown with grass seed or 
oats, and when the stalk comes to maturity it should 
not be cut, but suffered to remain as a kind of thatch 
to protect the facing from the weather. 

75. Fascine revetment. A fascine (Fig. 32) is a 
bundle of twigs closely bound up. There are two 

4 


38 


sizes of fascines; one size is nine inches in diame¬ 
ter, and about ten feet long; the other, which is 
generally termed a soucisson, is twelve inches in 
diameter and twenty feet long; it is chiefly used 
for the revetments of batteries. 

76. To make a fascine, straight twigs are select¬ 
ed, between the thickness of the little finger and 
thumb, the longer the better; they should be strip¬ 
ped of the smaller twigs. A machine, termed a 
fascine horse , is put up, by driving two stout poles 
obliquely into the ground about two feet, so as to 
cross each other about two feet above the ground, 
where they are firmly tied together ; as many of 
these supports as may be required are put up in a 
straight line, about eighteen inches apart; this 
forms the horse on which the twigs are laid to be 
bound together. 

77. Another machine, termed a fascine choker, 
is formed of two stout levers about five feet long, 
connected near their extremities by a chain or 
strong cord, which should be long enough to pass 
once round the fascine, and be drawn tight by means 
of the levers. 

78. The twigs are laid on the horse, with their 
large and small ends alternating; the choker is 
applied to bring them together; and they are bound 
by withes , or gads, made of tough twigs, properly 
prepared by untwisting the fibres over a blaze, so as 
to render them pliant; or else stout rope yarn may 
be substituted for them. The gads are placed 
twelve inches apart, and every third or fourth one 
should be made with an end about three or four feet 
long, having a loop at the extremity to receive a 
oicket through it; this picket is termed an anchor¬ 
ing picket, its object being to secure the fascine 
firmly to the parapet. 


39 


79. To form the revetment, the first row of fas¬ 
cines (Fig. 23) is imbedded about half its thick¬ 
ness below the tread of the banquette, and is secured 
Dy means of the anchoring pickets, and also by 
several pickets driven through the fascine itself 
about twelve inches into the earth. The knots of 
the withes are laid inside, and the earth of the para¬ 
pet is well packed behind the fascine. A second 
row is laid on the first, so as to give the requisite 
interior slope; it should break joints with the first 
row, and be connected with it by several pickets 
driven through them both. The other rows are laid 
with similar precautions ; and the parapet is usually 
finished at top by a course of sods. 

80. Hurdle revetment. This revetment is made 
by driving poles (Fig. 24), in the same direction as 
the interior slope, into the banquette, about eighteen 
inches below the tread, and then forming a wicker¬ 
work, by interlacing twigs between them in a simi¬ 
lar manner to basket work. 

The poles should be nine inches apart, their 
diameter about one-and-a-half inches. They should 
be secured to the parapet by long withes and an¬ 
choring pickets. The top twigs should be bound 
together by withes. 

81. Gabion revetment. The gabion (Fig. 25) 
is a round basket of a cylindrical form, open at 
each end, its height is usually two feet nine inches, 
and diameter two feet. 

82. To form a gabion, a directing circle is made 
of two hoops, the difference between their radii 
being such, that, when placed concentrically, there 
shall be about one-and-three-quarter inches between 
them. They are kept in this position by placing 
small blocks of wood between them, to which they 
are tied with packthread. The directing circle is 


40 


..aid on the ground, and seven or nine pickets, about 
one inch in diameter and three feet long, are driven 
into the ground between the hoops, at equal dis¬ 
tances apart; the directing circle is then slipped up 
midway from the bottom, and confined in that posi¬ 
tion. Twigs half an inch in diameter, and as long 
as they can be procured, are wattled between the 
pickets, like ordinary basket work ; when finished 
within about one-and-a-half inches of the top, the 
gabion is placed with the other end up, the directing 
circle is taken off, and the gabion is completed with¬ 
in the same distance from the other extremities of 
the pickets. The wicker work at the two ends is 
secured by several withes, and the ends of the pick¬ 
ets being brought to a point, the gabion is ready for 
use. 

83. The gabion revetment is seldom used except 
for the trenches in the attack of permanent works, 
where it is desirable to place troops speedily un¬ 
der cover from the enemy’s case shot and muske¬ 
try. When used for field works (Fig. 26), a fas¬ 
cine is first laid partly imbedded below the tread of 
the banquette ; the gabion, which is placed on end, 
rests on this, so as to give it the requisite slope ; it 
is filled with earth, and the parapet is raised behind 
it, and another fascine is laid on top, and in some 
cases two. 

84. Plank revetment. This revetment may be 
made by driving pieces of four-inch scantling about 
three feet apart, two feet below the tread of the 
banquette, giving them the same slope as the inte¬ 
rior slope. Behind these pieces, boards are nailed 
to sustain the earth. 

85. Sand bags are sometimes used for revetments 
when other materials cannot be procured; though 
their object, in most cases, is generally to form a 


4l 


speedy cover for a body of men. They are usually 
made of coarse canvass; the bag-, when empty, is 
two feet eight inches long, and one foot two inches 
wide ; they are three-fourths filled with earth, and 
the top is loosely tied. From their perishable na¬ 
ture, they are only used for a temporary purpose, as 
when troops are disembarked on an enemy’s coast. 

86. Scarp revetment. This revetment (Fig. 27) 
is formed of a framework of heavy timber, and is 
used only for important field forts. A piece, termed 
a cap , or cap-still, is imbedded in a trench made 
along the line of the berm ; other pieces, termed 
land-ties, are placed in trenches perpendicular to the 
cap, with which they are connected by a dove-tail 
joint; they are about eight or ten feet asunder 
Cross pieces are halved into the land-ties about two 
feet from their extremities, and two square piles, 
about five feet long, are driven in the angles between 
.the land-ties and cross pieces ; inclined pieces, whic-h 
serve as supports to the cap, are mortised into its 
under side at the same points as the land-ties. 
These supports usually receive a slope of ten per¬ 
pendicular to one base; they generally rest on a 
ground-sill at the bottom of the ditch, to which they 
are mortised; this sill being held firm by square 
piles. The ground-sill may be omitted, by driving 
the supports below the bottom of the ditch. 

Behind this framew r ork, thick plank, or heavy 
scantling, is placed side by side, having the same 
slope as the supports ; or else a rabate may be made 
in the cap and ground-sills, and the scantling be let 
in between these two pieces serving as a support to 
the cap. This is the more difficult construction, 
but it is the better, since, should the heavy supports 
be cut aw r ay, the cap will still be retained in its 
place. 


4 - 


42 


87. Scarp revetments are sometimes formed by 
laying heavy timber in a horizontal position; but 
this method is bad, as it enables the enemy to gain 
a foot-hold by thrusting their bayonets between the 
joints. 

88. The length of the land-ties should be at least 
equal to two-thirds the depth of the ditch. 

89. The counterscarp is seldom reveted. A 
framework similar to that for the scarp might be 
used, and thick boards, laid horizontally, be substi¬ 
tuted for the inclined scantling. 

90. When a scarp revetment is made, the exca¬ 
vation of the ditch must be conducted in a different 
manner from that already explained. In this case, 
after the cap-sill and land-ties are laid, the excava¬ 
tion is continued to the bottom of the ditch, by re¬ 
moving only earth enough to allow the framework 
to be put up. A scaffolding of plank is then raised 
in the ditch on which the earth, that remains to be 
excavated, is thrown, and from there on the berm. 



CHAPTER VII. 


ACCESSORY, OR SECONDARY MEANS OF DEFENCE. 

100. The means employed as accessory usually 
consist ef artificial obstacles, so arranged as to de¬ 
tain the enemy in a position where he will be greatly 
cut up by the fire of the work. 

101. Anything may be regarded as an obstacle to 
the enemy by which his attention is diverted from 
the assailed to his own situation; but no obstacle 
will be of much serv ice to the assailed which is not 
within good striking distance of his weapons. The 
proper disposition, therefore, of obstacles, is in ad¬ 
vance of the ditch within short musket ranore. 

102. Marshes, water courses, wet ditches, preci¬ 
pices, &c., may be regarded as obstacles, if they are 
sufficient in themselves to stop the enemy’s pro¬ 
gress. But, however strong, they are not solely to 
be relied on ; as the strongest natural position may 
be carried if not vigilantly guarded. 

103. In placing the ground around a work in a 
defensive attitude, every means should be taken to 
reduce to the smallest possible number the points 
by which the enemy may approach ; so that, by ac¬ 
cumulating the troops on the weak points, a more 
vigorous defence may be made. In making this 
arrangement, equal care should be given to every¬ 
thing that, affording a shelter to the enemy, would 
enable him to approach the work unexposed to its 
fires. To prevent this, all hollow-roads, or dry 
ditches, which are not enfiladed by the principal 
works, should be filled up, or else be watched by a 
detachment, covered by an advanced work. All 


44 


trees, underwood, hedges, enclosures, and houses, 
within cannon range, should be cut down and 
levelled, and no stumps be allowed higher than two 
feet. Trees beyond cannon range should not be 
felled; or if felled, they should be burnt, to prevent 
the enemy’s movements being concealed. 

104. If there are approaches, such as permanent 
bridges, fords, and roads, which may be equally ser¬ 
viceable to the assailed and to the enemy, they 
should be guarded with peculiar care ; and be ex¬ 
posed to the enfilading fire of a work especially 
erected for their defence. 

105. The principal artificial obstacles are trous- 
de-loup , or military pits ; abattis; palisades ; f raises ; 
sloccades ; chevaux-de-frise; small pickets; entangle¬ 
ments ; crows-feet; inundations; and mines. 

106. Trous-de-loup. (Fig. 28.) These are pits 
in the form of an inverted truncated cone, or qua¬ 
drilateral pyramid ; their diameter at top is six feet, 
their depth six feet, and width at bottom eighteen 
inches. A stake is, in some cases, planted firmly 
in the bottom, its top being sharpened, and the point 
a few inches below the upper circle. 

107. Trous-de-loup are generally placed in three 
rows, in quincunx order, a few yards in front of the 
ditch. They are readily laid out by means of an 
equilateral triangle, formed of cords, the sides of the 
triangle being eighteen feet; the angular points 
mark the centres of the pits. The earth taken 
from them is spread over the ground between them, 
and is formed into hillocks to render the passage 
between as difficult as possible. If brush wood, or 
light hurdles, can be procured, the pits may be made 
narrower, and covered with the hurdles, over which 
a layer of earth is spread. 


45 


Trous-de-loup are sometimes p.aced in the^ditch; 
in this case their upper circles touch. 

108. This obstacle is principally serviceable 
against cavalry. 

109. Abattis. (Fig. 21.) The large limbs of 
trees are selected for an abattis. The smaller 
branches are chopped off, and the ends, pointed and 
interlaced with some care, are presented towards 
the enemy. The large end of the limb is secured 
to the ground by a crotchet-picket , and may be partly 
imbedded to prevent its being readily torn up. 

One of the best methods of forming an abattis, 
and which is peculiarly adapted to strengthen the 
skirts of a wood occupied by light troops, is to fell 
the trees so that their branches will interlace, cutting 
the trunk in such a way that the tree will hang to 
the stump by a portion uncut. The stumps may 
be left high enough to cover a man in the act of 
firing. 

110. Abattis are placed in front of the ditch ; in 
this position they must be covered from the enemy’s 
fire by a small glacis. They are sometimes placed 
in the ditch against the counterscarp. 

111. This is an excellent obstacle in a wooded 
country, and admits of a good defence, if a slight 
parapet is thrown up behind it. The parapet may 
be made of the trunks of trees laid on each other 
with a shallow ditch, or trench, behind them ; the 
earth from which is thrown against the trunks. In 
an open position it may be relied on as a security 
against a surprise, particularly of cavalry. 

112. Palisades. (Fig. 23.) A palisade is a 
stake about ten feet long, and of a triangular form, 
each side of the triangle being eight inches. The 
trunks of straight trees should be selected for pali¬ 
sades. The diameter of the trunk should be from 


46 


sixteen to twenty inches. The trunk is sawed into 
lengths of ten-and-a-half feet, and is split up into 
rails, each length furnishing from five to seven rails. 
The palisade is pointed at top, the other extremity 
may be charred if the wood is seasoned, otherwise 
the charring will be of no service. A palisading 
is a row of palisades set in the ground, either verti¬ 
cally, or slightly inclined towards the enemy. To 
plant the palisades, a trench is dug three feet deep; 
they are then placed about three inches asunder, 
with an edge towards the enemy. Each palisade is 
nailed to a strip of thick plank, termed a riband , 
placed horizontally about one foot below the ground ; 
another riband is placed eighteen inches below the 
top. The earth is firmly packed in the trench. 

113. A palisading is sometimes used as a prima¬ 
ry means of defence, particularly for low w T orks. A 
banquette is thrown up for this purpose against it; 
the tread of the banquette being six feet below the 
top of the palisading, and four feet three inches 
below the upper riband. 

114. As an obstacle, it is best placed at the foot 
of the counterscarp ; the points being twelve inches 
below its crest, or else covered by a small glacis. 
In this position the palisading fulfils all the condi¬ 
tions of an efficient obstacle ; it is under the fire of 
the work; covered from the enemy’s fire ; will not 
afford a shelter to the enemy; and cannot be cut 
down without great difficulty. 

115. Fraise (Fig. 24.) This obstacle is formed 
of palisades, placed, in juxtaposition, either horizon¬ 
tally, or slightly inclined. The best position for a 
fraise is on the berm, or a little below it, so as to 
be covered by the counterscarp crest. The part of 
the fraise under [he parapet is termed the tail, and 
is about five feel long. To make a fraise, a hori- 


* 











■ 






















/ 


EXPLANATIONS OF PLATE III. 

Fig. 19. Shows the profile of a work in process of construction. 

Fig. 20. Shows the plan and cross section of sods. 

Fig. 21. Shows the profile of a work with a sod revetment; and 
a plan of the sod work— a being the headers of the 
bottom layer, and b those of the next layer. 

Fig. 22. Shows the elevation of a fascine horse, a, b; and the 
choker, c, d, applied to the fascine : f shows the di¬ 
mensions of the fascine, and its anchoring gads. 

Fig. 23. Shows a profile of a work with a fascine revetment, 
and palisades in its ditch. 

Fig. 24. Shows a profile of a work with a hurdle revetment and 
a fraise. 

Fig. 25. a shows the elevation of a gabion, half finished; and 
b the plan of the directing circle. 

Fig. 26. Shows the profile of a work with a gabion revetment; 

small pickets in its ditch ; and an abattis in front of 
the ditch, covered by a glacis. 

Fig. 27. Shows a plan and section of a timber revetment; b b' 
is the cap; d d’ the sill; c c' uprights let into b and 
d ; a A f the land-ties, dove-tailed into b, and confined 
bv the cross pieces e k', halved into them, and by 
the square short piles f ; go' are the piles to retain 
the sill. 




































































































































47 


zontal piece of four-inch scantling, termed a cush¬ 
ion, is first laid parallel to the berm ; each palisade 
is nailed to this, and a thick riband is nailed on tcp 
of the fraise near the end. 

116. The point of the fraise should be at least 
seven feet above the bottom of the ditch, and should 
not project beyond the foot of the scarp, so as not to 
shelter the enemy from logs, stones, &c., rolled 
from the parapet into the ditch. 

117. Stoccade. Trunks of small trees from nine 
to twelve inches in diameter, and twelve feet long, 
are selected to form a stoccade. They are planted 
in juxtaposition, in a similar manner to a palisading, 
and are used for the same purposes. The manner 
of arranging a stoccade, which is also sometimes 
termed a picket, as a primary defence, will be de¬ 
scribed in another chapter. 

118. Chevaux-de-frise. A cheval-de-frise (Fig. 
29) consists of a horizontal piece of scantling of a 
square, or hexagonal form, termed the body, about 
nine feet long, which is perforated by holes two 
inches in diameter, and five inches apart; round 
staffs, ten feet long, and two inches in diameter, 
termed lances, shod with fron points, and inserted 

. into the body, so as to project equally from it. At 
one end of the body a ring and chain arc attached; 
at the other a hook and chain; for the purpose of 
attaching several together, forming a chevaux-de- 
frise. 

119. The square is the best form for the body, it 
requires only five-inch scantling, whereas the hexa¬ 
gon will require twelve-inch timber. 

120. The chevaux-de-frise is not much in use as 
an obstacle, owing to the difficulty of making it. 
It is a good defence against cavalry; and on rock 
may supply the place of palisades; but even here 


48 


an abattis would be more effective, and generall) 
more readily formed. 

121. Small pickets. This obstacle (Fig. 26) con¬ 
sists of straight branches of tough wood cut into 
lengths of two-and-a-half, or three feet. They are 
driven into the ground, in a quincunx order, about 
twelve inches apart, and project irregularly above it, 
not more than eighteen inches. Interlaced with 
cords, grape-vines, brambles, prickly shrubs, &c., 
they form an excellent entanglement. 

122. The crows-foot is formed of four points of 
iron, each spike about two-and-a-half inches long, 
and so arranged, that when thrown on the ground 
one of the points will be upwards. They are a 
good obstacle against cavalry, but are seldom used. 
Boards, with sharp nails driven through them, may 
supply the place of crows-feet. The boards are 
imbedded in the ground, with the sharp points pro¬ 
jecting a little above it. 

123. Inundations. This obstacle is formed by 
damming back a shallow water-course, so as to make 
it overflow its valley. To be effective, an inunda¬ 
tion should be six feet deep. When this depth can¬ 
not be procured, trous-de-loup, or else short ditches, 
placed in a quincunx order, are dug, and the whole . 
is covered with a sheet of water, which, at the 
ditches, must be at least six feet in depth. 

124. The dams used to form an inundation are 
made of good binding earth. They cannot, in ge¬ 
neral, be raised higher than ten feet; they need not 
be thicker than five feet at top, unless they are ex¬ 
posed to a fire of artillery, in which case they should 
be regulated in the same way as a parapet. The 
slope of the dam down-stream should be the natu¬ 
ral slope of the earth; but up-stream the slope 
should h?.ve a base twice that of the natural slope. 


49 


Sluices are made in the dams, in a similar manner 
to the sluices of a mill-dam, for the purpose of regu¬ 
lating the level of the water in the pool above, in 
case of heavy rains. Waste-wiers are also service¬ 
able for the same purpose, but unless carefully made 
they may endanger the safety of the dam. 

125. The distance of the dams apart will depend 
on the slope of the stream. The level of each 
pool should be at least eighteen inches below the 
top of the dam, and the depth of water below each 
dam should be at least six feet. These data will 
suffice to determine the centre line, or axis of each 
dam. 

126. Artificial inundations seldom admit of being 
turned to an effective use, owing to the difficulties 
in forming them, and the ease with which they can 
be drained by the enemy. But when it is practi¬ 
cable to procure only a shallow sheet of water, it 
should not be neglected, as it will cause some ap¬ 
prehension to the enemy. In some cases, by dam¬ 
ming back a brook, the water may be raised to a level 
sufficient to be conducted into the ditches of the 
work, and render some parts unassailable. The 
ditches in such cases should be made very wide, 
and to hold about a depth of six feet. During 
freezing weather the ice should be broken in the 
middle of the ditch, and a channel of twelve feet at 
least be kept open, if practicable. The ice taken 
out should be piled up irregularly on each side of 
the channel; and, as a farther precaution against 
a surprise, water should be thrown on the parapet 
to freeze. 

127. Mines. Attempts at applying mines to the 
defence of field works have seldom proved success¬ 
ful, owing to the rapid character of the assault; 
from which the mines a re usually sprung too soon 

5 


50 


or too late; so that the only effect that can be 
counted upon for their use is the panic they may 
create. 

* 128. There is one species of mine denominated 

a stone-fovgasse, whic-h it is thought might be suc¬ 
cessfully applied to the defence of the ditches and 
salients of field works. To make this mine (Fig. 
30), an inclined funnel-shaped excavation is made, 
to the depth of five or six feet, at the bottom of the 
funnel a box containing fifty-five pounds of powder 
is placed, with which a powder-hose communicates. 
A strong shield of wood, formed of battens well 
nailed together, is placed in front of the box; and 
three or four cubic yards of pebbles, or an equal 
weight of brick bats, or other materials, are filled 
in against the shield. Earth is then well rammed 
around the shield on top and behind, to prevent the 
explosion from taking place in the wrong direction. 
A fougasse of this size, when sprung, will scatter 
the pebbles over a surface sixty yards in length, and 
seventy yards in breadth. 


CHAPTER VIII. 


INTERIOR ARRANGEMENTS. 

129. Under the head of interior arrangements 
is comprised all the means resorted to within the 
work to procure an efficient defence ; to preserve 
the troops and the materiel from the destructive 
effects of the enemy’s fire; and to prevent a 
surprise. 

130. The class of constructions required for the 
above purposes, are batteries; powder-magazines; 
traverses; shelters; enclosures for gorges , and out¬ 
lets ; interior safety-redoubt, or keep; and bridges of 
communication. 

131. All arrangements made for the defence, 
with musketry and artillery, belong to what is termed 
the armament. 

132. The armament with musketry is complete 
when the banquette and the interior and superior 
slopes are properly arranged, to enable the soldier 
to deliver his fire with effect; and to mount on the 
parapet to meet the enemy with the bayonet. For 
this last purpose stout pickets may be driven into 
the interior slope, about midway from the bottom, 
and three feet apart. The armament with artillery 
is, in like manner, complete, when suitable means 
are taken to allow the guns to fire over the parapet, 
or through openings made in it; and when all the 
required accessories are provided for the service of 
;he guns. 

133. The armament with artillery is a subject of 
great importance, because it is not equally adapted 
to all classes of works. Experience has demon- 


52 


Btrated that the most efficient way of employing 
artillery, is in protecting the collateral salients by a 
well directed flank and cross fire, which shall not 
t leave untouched a single foot of ground within its 
range, over which the enemy must approach. It 
has moreover shown, that a work with a weak pro¬ 
file affords but little security to artillery within it; 
for artillery cannot defend itself, and such a work 
can be too easily carried by assault to offer any 
hope of keeping the enemy at a distance long 
enough to allow the artillery to produce its full 
effect. 

134. The best position for artillery is on the 
flanks and salients of a work ; because from these 
points the salients are best protected, and the ap¬ 
proaches best swept; and the guns should be col¬ 
lected at these points in batteries of several pieces; 
for experience has likewise shown, that it is only by 
opening a heavy, well-sustained fire on the enemy’s 
columns, that an efficient check can be given to them. 
If only a few files are taken off, or the shot passes 
over the men, it rather inspires the enemy with confi¬ 
dence in his safety, and with contempt for the de¬ 
fences. 

135. Batteries. The term battery is usually ap¬ 
plied to a collection of several guns; it is also used 
in speaking of the arrangements made of a parapet 
to enable the guns to fire over it, or through openings 
in it; as a barbette battery , an embrasure battery , &c. 
Two kinds of batteries are used in the defence of 
intrenchments, the barbette battery and the embra¬ 
sure battery. 

136. The barbette is a construction by means of 
which a piece can fire over a parapet. It consists 
of a mound of earth, thrown up against the interior 
slope ; the upper surface of which is level, and two 


53 


feet nine inches below the interior crest for guns 
of small calibre, and four feet for heavy guns. If 
the barbette is raised behind a face, its length should 
be sufficient to allow sixteen-and-a-half to eighteen 
feet along the interior crest for each gun; and its 
depth, or the perpendicular distance from the foot of 
the interior slope to the rear, should be twenty-four 
feet, for the service of the guns. The earth of the 
barbette at the rear and sides receives the natural 
slope. To ascend the barbette, a construction, 
termed a ramp, is made ; this is an inclined plane 
of earth, which connects the top of the barbette 
with the terre-plein. The ramp is ten feet wide at 
top, and its slope is six base to one perpendicular. 
The earth at the sides receives the natural slope. 
The ramp should be at some convenient point in the 
rear, and take up as little room as possible. 

137. As barbettes are usually placed in the sa¬ 
lients, an arrangement is made for the guns to fire 
in the direction of the capital. The construction in 
this case is somewhat different from the preceding. 
A pan-coupe of eleven feet (Fig. 31) is first made ; 
from the foot of the interior slope at the pan-coupe, 
a distance of twenty-four feet is set off along the 
capital; at the extremity of this line a perpendicu 
lar is drawn to the capital; and five feet are set off 
on this perpendicular on each side of the capital; 
from these points, on the perpendicular, a line is 
drawn perpendicular to each face respectively; the 
hexagonal figure, thus laid out, is the surface of the 
barbette for one gun. The ramp in this case is 
made along the capital. 

138. If three or more guns are placed in the sa¬ 
lient, a pan-coupe is formed as in the last case ; and 
twenty-four feet (Fig. 32) are in like manner set 
off on the capital ; but instead of proceeding as in 

5* 


54 


the last case, a perpendicular is drawn from this 
point to each face, and the pentagonal space, thus 
enclosed, will be taken for the gun in the salient; 
from the perpendiculars last set off*, as many times 
sixteen-and-a-half feet will be set off*, on the interior 
crest of each face, as there are guns required : this 
will give the length of the barbette along each face ; 
the depth will be made twenty-four feet, and the two 
will be united in the salient. One or more ramps 
may be made as most convenient. 

139. The advantages of the barbette consist in the 
commanding position given to the guns, and in a 
very wide field of fire; on these accounts the sa¬ 
lients are the best positions for them. Their defects 
are, that they expose the guns and men to the ene¬ 
my’s artillery and sharpshooters. 

Light guns, particularly howitzers, are the best 
v or arming barbettes; because the hollow projectile 
of the latter is very formidable, both to the enemy’s 
columns and to his cavalry ; and when his batteries 
are opened against the salients, the light pieces can 
be readily withdrawn. 

140. The embrasure (Fig. 33) is an opening 
made in the parapet for a gun to fire through. The 
bottom of the embrasure, termed the sole , is two 
feet nine inches, or four feet above the ground, on 
which the wheels of the carriage rest, according to 
the size of the gun; it slopes outwards to allow the 
^un to be fired under an inclination, the base of this 
ilope should never be less than six times the alti¬ 
tude ; the interior opening, termed the mouth, is 
from eighteen inches to two feet wide, according to 
the calibre of the gun, and is of a rectangular form; 
the embrasure widens towards the exterior, which 
widening is termed the splay; the manner in 
which the splay is regulated, is by producing the 




. 

- 

*- 





























PLATE IV. 


EXPLANATIONS OF 

Figs. 28, 29. Show a plan and section of an arrangement of 
conical trous-de-loup; small pyramidal pits, with 
pickets; and an advanced glacis and abattis. 

Fig. 30. Shows an elevation, b, and a cross section, a, of a che 
val-de-frise. 

Fig. 31. Shows a plan and section of a stone fongasse ; a a' is 
the powder-box and the shield; b b' the stones in 
the funnel; c cJ the powder-hose to fire the fongasse, 
d d' the powder-trough tamped with sand-bags, 
which, with the arrangement of the earth, as shown 
in the section, are to prevent the load from acting to 
the rear. 

Fig. 32. Shows the plan of a barbette for one gun ; a is the sur 
face of the barbette ; b that of the ramp; c the plat¬ 
form ; d the superior slope at the pan-coup6. 

JVete.—On the section m n the letters b t , c*, d', cor¬ 
respond to the same on the plan. 

Fig E. Shows a platform of beams; a is the heurter; b the 
wheel supports; c the trail supports; d d cross sup¬ 
ports of b and c, confined by pickets 

































































































































































55 


sole to the exterior slope of the parapet, and making 
this exterior line, measured on the sole, equal to 
half the distance between the inner and outer lines 
of the sole. This construction makes the sole a 
trapezoidal figure; the side of the trapezoid, on the 
interior being eighteen inches, or two feet; the op¬ 
posite side being equal to half the perpendicular 
distance between the two sides. The line which 
bisects the sole is termed the directrix of the em¬ 
brasure ; the sides of the embrasure, termed the 
cheeks, are laid out, by setting off two points on the 
exterior crest of the parapet, one on the right, the 
other on the left of the sole, so that the horizontal 
distance of these points from the sole shall be equal 
to one-third their height above it. Lines are then 
drawn, on the exterior slope, from these points to 
the exterior points of the sole; lines are in like 
manner drawn from the same points, on the superior 
slope, to the upper points of the mouth, on the in¬ 
terior crest. These four lines form the boundaries 
of the two cheeks on the superior and exterior 
slopes. 

141. When the directrix is perpendicular to the 
direction of the parapet, the embrasure is termed 
direct; when the directrix makes an acute angle 
with it, the embrasure is termed oblique. 

142. The manner of laying out an oblique em¬ 
brasure is similar to the direct; the mouth is of a 
rectangular form, but is made wider in proportion to 
the obliquity, in order that the part of the embrasure, 
which corresponds to the muzzle of the gun, may be 
nearly of the same width in both the direct and 
oblique embrasures. The exterior width of the sole 
is made equal to one half the length of the directrix, 
measured on the sole. The cheeks are laid out as 
in the last case. 


56 


143. The muzzle of a gun should enter al 
least six inches into the embrasure, to prevent the 
blast from injuring the cheeks ; this limits the ob¬ 
liquity of the directrix to about 60° for long guns. 

144. The height of the cheeks must not be more 
than four feet, for the same reason; it will, there¬ 
fore, in some cases, be necessary to raise the ground 
on which the wheels rest. 

145. The parapet of a battery is usually termed 
the epaulment. The interior face of the epaulment, 
and the cheeks of the embrasures, are riveted in 
the usual manner. That part of the interior face 
which lies below the chase of the gun is termed the 
genouillere. The mass of earth between two em¬ 
brasures is termed a merlon. 

146. The embrasures are generally cut out after 
the epaulment is thrown up. If their position is de¬ 
cided upon beforehand, they may be roughly formed at 
first, and be finished after the epaulment is made. 

147. The advantages of embrasures are, that 
the men and guns are less exposed than in a 
barbette battery. Their principal defects are, that 
they have a very limited field of fire; they weaken 
the parapet; and present openings through which 
the enemy may penetrate in an assault. Owing 
to their limited field of fire, they are chiefly used 
for the protection of particular points; as to flank a 
ditch, protect a salient, enfilade a road, &c. The most 
suitable position for them in a work is on the flanks. 

148. Platforms. When a gun is fired often in 
the same direction, the ground under the wheels is 
soon worn into ruts; it is to prevent this, that plat¬ 
forms of timber are used in such cases. 

149. The shape of the platform is usually a 
rectangle ; in some cases, where a wide field of fire 
is to be obtained, the form is a trapezoid. The 


57 


rectangular platform (Fig. 33) is ten feet wide, and 
seventeen feet long, for siege pieces ; and nine feet 
wide and fifteen long, for field guns. It consists of 
three sleepers of six-inch scantling, either fifteen or 
seventeen feet long, which are laid perpendicular to 
the direction of the epaulment, and are covered with 
two-inch plank, twelve inches wide, and cut into 
lengths of nine or ten feet. Between the ends of 
the sleepers, and the foot of the genouillere, a piece 
of eight-inch scantling, nine feet long, termed a 
heurler, is laid; it should project about six inches 
above the platform, and be bisected by the directrix. 
The object of the heurter is to prevent the wheels 
from being run against the revetment, and also to 
give the gun its proper direction, particularly in 
night firing. 

150. To lay a platform, the earth on which it 
is to rest should be well rammed and levelled: 
three trenches are then made for the sleepers, two 
of which should be placed under the wheels, and 
the middle one under the trail. The sleepers are 
laid flush with the ground, and firmly secured by 
pickets driven at their sides and ends, and the earth 
is solidly packed in the trench around them; the 
plank is then laid and secured by nails, or some 
other fastenings. 

151. If the platform is for direct firing, with full 
charges, the tail may be made six inches higher 
than the front to break the recoil; in all other cases 
it should be horizontal. 

152. A platform may be constructed simply of 
three pieces of timber (Fig. 31), one under each 
wheel, and one under the trail, firmly secured by 
pickets, and connected by cross pieces, into which 
they are halved. 


58 


152. For barbettes, the platform may be dispensed 
with; or, if used, the whole surface nearly of the 
barbette should be covered. 

153. If the platform is made of a trapezoidal 
form, it will require five sleepers. 

154. Powder magazines. The main objects to be 
attended to in a powder magazine are, to place it in 
theposition least exposed to the enemy’s fire; to make 
it shot proof; and to secure the powder from moisture. 

155. If there are traverses, such, for example, 
as are used in defilement, the magazines may be 
made in them ; or they may be placed at the foot 
of a barbette ; or, in dry soils, be made partly under 
ground. 

156. The magazine should be at least six feet 
high, and about the same width within ; its length 
will depend on the quantity of ammunition. It 
may be constructed of fascines, gabions, or coffer- 
work , or any means found at hand may be used 
which will effect the end in view. 

157. If fascines are used, the sides (Fig. 34) 
should slope outwards to resist the pressure of the 
earth; the fascines should be firmly secured by 
pickets, and anchoring withes. The top may be 
formed by a row of joists, of six-inch scantling, 
placed about iwo-and-a-half feet apart; these should 
be covered by two layers of fascines laid side by side, 
and the whole be covered in by at least three feet 
thickness of earth. The bottom should be covered 
by a flooring of joists and boards; a shallow ditch 
being left under the flooring, with a pitch towards 
the door of the magazine, to allow any water that 
might leak through to be taken out. A thatch of 
Btraw might be used on the inside, but it is some¬ 
what dangerous, owing to its combustibility; hides 




59 

or tarpaulins are better, and will keep out the mois¬ 
ture more effectually. 

158. A coffer-work is formed by making frames 
(Fig. 35) of six-inch scantling; each frame is 
composed of two uprights, termed stanchions, and a 
cap and ground-sill, well nailed together; it is six 
feet wide, and six feet high in the clear. These 
frames are placed upright, and parallel to each 
other, about two-and-a-half feet apart; they are 
covered on the top and sides by one-and-a-half-inch 
plank which is termed a sheeting. The magazine 
otherwise is constructed as in the last case. 

159. When gabions are used, a hole is usually 
dug in the ground to form a part of the magazine ; 
the gabions (Fig. 36) are placed in two rows, side 
by side, around the hole, and are filled with earth. 
The top is formed as in the case of fascines. 

160. The mouth of the magazine is covered by a 
splinter proof shelter. This is constructed (Fig. 

37) by taking scantling eight by ten inches, cut 
into suitable lengths, and placing it in an inclined 
position, so as to cover the mouth, and leave an easy 
access to it. The pieces, usually, are inclined 45°, 
and are placed side by side; they are covered by at 
least two feet of earth, or sods ; and hides or tar¬ 
paulins are thrown over the whole. 

161. Splinter proof blinds are mainly intended to 
afford a shelter against the fragments of hollow pro¬ 
jectiles that explode in the work. They may be 
used as a kind of barrack for the troops; and to 
store provisions, &c. 

162. Traverses. Those which are constructed 
to cover the flanks of the guns from an enfilade fire, 
are usuaLy what are termed gabionades. To form 
a gabionade, gabions are placed in a row (Fig. 

38) , side by side, enclosing a rectangular space of 


60 


about twelve feet in width from out to out, and about 
twenty-four feet in length, perpendicularly to the 
epaulment. A second row is placed within this 
and touching it. The area thus enclosed is 
filled in with earth, to a level with the top of the 
gabions. Four rows of large fascines are next laid 
on the gabions, to support a second tier consisting 
of one row. The second tier is filled in like the 
first, and the earth is heaped up on top, making the 
gabionade nearly eight feet high. The work will 
be expedited by throwing up the greater part of the 
earth before placing the second tier. Splinter proof 
traverses may be made by placing three thicknesses 
of gabions side by side filled with earth, with a 
second tier of two thicknesses on top. 

163. Enclosures for gorges and outlets. A stoc- 
cade is the best enclosure for the gorge of a work. 
The outline (Fig. 39), or plan of the gorge, should 
be a small bastion front, for the purpose of obtaining 
a flank defence. 

164. The trunks for the stoccade (Fig. 40) should 
be ten or twelve inches in diameter, and eleven feet 
*in length. It will be best to square them on two 
sides, so that they may have about four inches of 
surface in contact. The top of the stoccade should 
be at least eight feet above the ground. To arrange 
it for defence, a banquette is thrown up against it 
on the interior; the height of the banquette one foot 
nine inches. A strip, about two feet in length, 
should be cut from the top of two adjacent trunks, 
with a saw, so that when they are placed side by 
side there shall be an opening at top, between them, 
eight inches wide on the interior, and twQ and a 
half inches on the exterior; this opening, through 
which the muzzle of the musket is run out, in firing, 
is termed a loop-hole. The distance between the 




EXPLANATIONS OF PLATE V 

Fig 33. Shows the plan of a barbette for three guns; the let¬ 
ters designate the same parts as in Fig. 3‘J. 

Fig. 33. (Bis.) Shows the arrangement of a Direct and Oblique 
Embrasure, with the common Platform. 

c d E f is a Section of the Epaulment. 

c i k d is the plan of the Sole; and a b is its position In 
elevation. 

o i p K is the plan of the Mouth, and a d is its elevation. 

i o a c is the plan of the left Cheek, and a d e b its eleva¬ 
tion. 

cd = Jab; g h = £ e f. 

a b and a b show the position of the Directrix in plan and 
elevation. 

M is the Merlon, or mass of earth between two embrasures. 

Fig. 34. Shows a cross section of a Powder Magazine made of 
fascines and timber. 

Fig. 35 a shows a longitudinal, and b a cross section of a Pow¬ 
der Magazine of coffer-work, covered with fascines 
and earth. 

Fig. 36 Shows a cross section of a Powder Magazine, the sides 
of which are formed of gabions, and the roof of tim¬ 
ber and fascines covered with earth. 






























































































61 


* 


loop-holes should be three feet. In this arrangement 
the bottom of the loop-holes will be six feet above 
the ground, on the exterior, to prevent the enemy 
from closing on them to stop them up, or use them 
in the attack. 

165. About four feet in front of the stoccade, a 
ditch is made twelve feet wide and three feet deep. 
The earth from the ditch is thrown up against the 
stoccade, in a slope, to the level of the bottom of the 
loop-hole, to prevent the enemy from attempting to 
cut down the stoccade. 

166. Outlets are passages made through a para¬ 
pet, or an enclosure of a gorge, for the service of 
the work. They should in all cases be made in the 
least exposed part of the work. Their width need 
not be more than six and a half feet, when used 
only for the service of the work; but when they 
serve as a common passage for wagons, &c , in the 
case of the intrenchment crossing a road, they 
should be at least ten feet wide. 

When cut through a parapet, the sides receive a 
slope of three perpendicular to one base, and are 
riveted with sods, &c. 

167. A gate, termed a barrier , serves as an en¬ 
closure to the outlet. The framework of the bar¬ 
rier is made like an ordinary gate (Fig. 41), con¬ 
sisting of two uprights, or stiles , a cross-piece, or 
rail , at top and bottom, and a swinging bar , or a 
diagonal brace. Upright palisades, about seven feet 
long and four inches thick, are spiked to the frame 
about four inches apart; they are finished at top with 
spikes. A barrier, thus constructed, will not offer a 
shelter to the enemy should he attempt to cut it away. 
The barrier is hung on hinges like an ordinary gate. 
The posts of the framework should be very solidly 
braced to support the weight of the barrier. 

u 


62 


A cheval-de-frise is sometimes used for a Darrier; 
it presents but a trifling obstacle. 

168. The outlet should be covered by a mask, 
thrown up either on the interior, or on the exterior, 
to prevent the enemy from firing through it into the 
work. A traverse (Fig. 42) is thrown across it, if 
placed on the interior. Sufficient space should be 
left between the traverse and the parapet for the pas¬ 
sage of a gun. The length of the traverse is ar¬ 
ranged to prevent the enemy from firing into the 
work, by an oblique fire through the outlet. The 
traverse may be of earth or of wood; in either case 
it should be arranged for defence to enfilade the 
outlet. In some cases, and it would generally be 
safest, a barrier is erected between the parapet and 
the traverse, on each side of the outlet. 

169. In very frequented passages, a redan (Figs. 
48, 49, &c.) or a lunette, is thrown up on the ex¬ 
terior to cover the outlet, and ensure its safety in 
case of surprise. 

170. Safety Redoubt. In enclosed works a place 
of retreat, into which the troops may retire in safety 
after a vigorous defence of the main work, will re¬ 
move the fears of the garrison for the consequences 
of a successful attack of the enemy, and will in¬ 
spire them with confidence to hold out to the last 
moment. 

171. This interior work, which may very pro¬ 
perly be termed the keep, can only be applied to 
works of large interior capacity. It may be formed 
of earth, or consist simply of a space enclosed by a 
defensive stoccade, or palisading. In either case it 
should be about four feet higher than the main 
work, to prevent the enemy from obtaining a plung¬ 
ing fire in it from the parapet of the main work. 

172. The best arrangement for the keep is the 


63 


construction termed the block-home . This work 
(Fig. 43) is made of heavy timber, either squared 
on two sides or four ; the pieces which form the 
sides of the block-house are either laid horizon¬ 
tally, and halved together at the ends, like an or¬ 
dinary log-house, or else they are placed vertically, 
side by side, and connected at top by a cap-sill. 
The sides are arranged with loop-hole defences ; and 
the top is formed by laying heavy logs, side by side, 
of the same thickness as those used for the sides, 
and covering them with earth to the depth of three 
feet. 

173. With regard to the details of the construc¬ 
tion, the timber for ihe sides should be twelve 
inches thick, to resist an attack of musketry, and 
to resist field-pieces two feet, in which case the 
sides are formed of two thicknesses of twelve-inch 
timber. If the timber is placed upright, each piece 
should be let into a mortise in the cap-sill; and 
every fourth piece of the top, at least, should be 
notched on the cap-sill, to prevent the sides from 
spreading out. 

174. The plan of the block-house must conform 
to its object generally; it may be square or rectan¬ 
gular. (Fig. 44.) If flank defences are required, 
its plan may be that of a cross. The interior 
height should not be less than nine feet, to allow 
ample room for loading the musket; this height 
will require that the timber of the sides shall be 
twelve feet long, in order to be firmly set in the 
earth. Sometimes a ground sill is placed under the 
uprights, but this is seldom necessary. The width 
may be only twelve feet in some cases, but it is bet¬ 
ter to allow twenty feet; this will admit of a camp 
hed of boards on each side, six-and-a-half feet 
wide, and a free space of seven feet. If cannon is 


64 


to be used for the defence, the width must be at 
least twenty-four feet; this will allow eighteen feet 
for the service of the gun, which is generally am¬ 
ple, and six feet for a defence of musketry on the 
opposite side. A greater width than twenty-four 
feet cannot well be allowed, because the bearing 
would be too great between the sides for tw’elve- 
inch timber; and even for a width of sixteen feet 
it would be well to support the top pieces, by plac¬ 
ing a girder under them resting on shores. 

175. The loop-holes are three feet apart; their 
interior dimensions are twelve inches in height, and 
eight inches in width for sides twelve inches thick; 
and twelve inches square for sides two feet thick. 
The width on the exterior, for the same thicknesses, 
will be two-and-a-half and four inches. The 
height of the loop-hole on the exterior will depend 
on the points to be defended ; it should admit of the 
musket being fired under an elevation and a de¬ 
pression. The height of the loop-hole above the 
exterior ground is six feet. 

176. Vents for the escape of the smoke are made 
over each loop-hole, between the cap-sill and the top 
pieces. 

177. The camp bed serves also as a banquette ; 
it is placed four feet three inches below the loop¬ 
hole, and has a slight slope of about eight inches 
inwards. 

178. The provisions, accoutrements, &c., are 
placed on shelves and racks attached to the shores 
and girders. 

179. The block-house is surrounded by a ditch, 
similar to the one used for a defensive stoccade. 
A strong door is made in one of the re-entering 
angles, and a slight bridge leads from it across the 
ditch. 


65 


180. It has been proposed to place a slight para¬ 
pet of earth on top of the block-house. It is 
thought that this accumulation of earth would be 
too heavy for the timbers, independently of leaving 
but little space for the defence. Perhaps a better 
arrangement might be made on top, similar to a de¬ 
fensive stoccade, the uprights being secured at 
bottom, between two pieces resting on the top 
pieces, and held firm by an arrangement of riband 
pieces and braces. 

181. It has also been proposed to place the inte¬ 
rior and exterior rows of uprights three feet apart, 
and to fill in between them with closely packed 
earth, for a defence against artillery. This method 
has been tried, and was found to be less solid than 
the one here laid down, independently of being 
more difficult to construct. 

182. The top pieces should in no case project 
more than twelve inches beyond the sides to admit 
of logs, &c., being rolled over on the enemy. 

183. The block-house is sometimes arranged 
with two stories, the corners or the sides of the 
upper story projecting over the sides of the lower. 
Either of these methods is sufficient for the de¬ 
fence of the lower story ; but the first is the best to 
procure a fire in the direction of its angles. It can 
only be used, however, as a defence against in¬ 
fantry. 

184. When artillery cannot be brought to bear 
against the top of the block-house, it may be con¬ 
structed like an ordinary floor, and be covered with 
nine or twelve inches of earth to guard against fire. 

185. The application of wood to the purposes 
of defence is one of paramount importance in our 
country. A block-house, surrounded by a defensive 
stoccade, is impregnable to the attack of infantry 

6 * 


66 


if properly defended, and is therefore peculiarly 
suitable to either wooded or mountainous positions, 
where a train of artillery cannot be taken without 
great labor, owing to the impediments that may be 
thrown in its way, by rendering the roads impassa¬ 
ble from obstructions easily obtained. In positions 
covered by extensive earthen works, such as those 
that would be required for the defence of the towns 
on our sea-board, and which would be occupied dur¬ 
ing a war, a defensive arrangement of the barracks 
for the troops, so that they might serve, in case of the 
main works being forced, as rallying points, under 
cover of which the main body of troops may retreat 
with safety, is a subject that commends itself to the 
serious attention of the engineer. From the details 
already entered into, an efficient combination for 
this purpose will suggest itself to the reader, with¬ 
out entering farther into particulars. 

186. Ditch defences. The surest defence for a 
ditch is a good flanking arrangement of the work 
itself; but as this is, in many cases, impracticable, 
owing either to the relief, or to the plan, flank de¬ 
fences must be procured by a construction made in 
the ditch. Several methods may be resorted to for 
this purpose, termed caponnieres , scarp and counter¬ 
scarp galleries. 

187. The caponniere is a work made across the 
ditch, and may be either single or double. A sin¬ 
gle caponniere is nothing more than a defensive 
stoccade, or palisading, made at the extremity of 
a ditch, as in the case of a redan. It will obvi¬ 
ously be of no service, unless the enemy is forced 
to attack it in front. 

188. A double caponniere (Fig. 45) is arranged 
to fire in two directions, and is usually placecl at 
the middle of the ditch which it is to protect. It is 






' 




















EXPLANATIONS OF PLATE VI. 


Fig. 37. Shows a cross section of a Splinter Proof Shelter laid 
against the side of a Traverse. The traverse is re¬ 
vetted with fascines, and the timber work is covered 
with sand bags and tarpaulins, or raw hides. 

Fig. 38. Shows the cross section of a Gabionade. 

Fig. 39. Shows the plan of a Lunette, with its gorge enclosed 
by a Stoecade, the plan of which is a small bastion 
front. 

Fig. 40. Shows the section and exterior elevation of a Defensive 
Stoecade. 

Fig. 41. Shows the plan and elevation of a Barrier. 

a a are the Posts to which the Gate is swung, a-nd at¬ 
tached, when closed. 
b b are the Uprights of the Gate, 
c c' the upper and lower Cross Pieces. 

D the Diagonal Brace. 
e the Bar of the Gate. 

Fig. 42. Shows a phin and section of the Outlet through the face 
of a work, covered by an interior Traverse, 
o is the Outlet or Passage through the parapet, 
p the Passage between the Traverse t, and the foot of the 
banquette. 

t is the Traverse, supposed of earth ; its banquette being 
ascended by steps, instea d of an ordinary slope, to save 
room. 

Figs. 43 44. Show the plan and section of a block-house of up¬ 
right timber. The plan is made to exhibit a portion of 
the top complete ; the timber covering of the top; the 
arrangement of the cap pieces ; a plan of the loop-holes ; 
and a plan of the camp-bed. Fig. 43 exhibits, in like 
manner, a cross section of the block-house and ditch ; 
with an interior and exterior elevation. 

Fig. 45. Shows a cross section of a double caponiere, with lour*- 
holes near the bottom of the ditch. 



- - I 


Section and Elevation on, 


K lent lion 


St it ion on ill li Tiff 30. 


Elrralioji 






ht.: 


r 


i'i 1.1.. 


( 

'sens'll^ 


r=“r 



















































































































































































67 

made in all respects like a block-house with upright 
sides ; its width may be only eight feet, and °its 
height the same. 

189. The bottom of the caponniere may be on 
the same level as the ditch, or be'low it; in the lat¬ 
ter case, the loopholes should not be more than 
eighteen inches above the level of the ditch, to pre¬ 
vent the enemy from using them against the as¬ 
sailed within. In the former, a small ditch should 
be made round the caponniere, and the earth from 
the ditch be thrown against its sides. 

190. The plan of the caponniere (Fig. 46) should 
be arranged to admit of being flanked by a defen¬ 
sive stoccade, placed at the foot of the scarp ; for 
this purpose the end next to the counterscarp should 
be in the form of a salient flanked by the stoccade. 
To prevent the enemy from jumping on the capon¬ 
niere, from the crest of the counterscarp, a space 
of at least twelve feet should be left between the 
two. Moreover, the top of the caponniere should 
be covered from the enemy’s artillery, either by the 
counterscarp crest, or by a glacis. 

191. The communication to the caponniere, from 
the work, may be by a timber gallery under the pa¬ 
rapet, formed of frames and a sheeting, similar to the 
construction used for a powder magazine. 

192. The counterscarp gallery (Fig. 47) consists 
of a framework, covered on top with a sheeting, 
which is placed within the counterscarp at the sa¬ 
lients. The front of the gallery is made of nine or 
ten-inch scantling, placed upright, and arranged 
with loophole defences; these pieces are connected 
at top by a cap-sill. Cross-pieces are notched on 
the cap-sill, about three feet apart; they are sup¬ 
ported by shores placed four feet from the front 
piece. The cross-pieces may project three feet be- 


yond the shores, and, if necessary, be braced from 
the shores. The gallery is covered on top by one- 
and-a-halfdnch sheeting; and behind in a similar 
manner, but only to the height of five feet above 
the bottom. This arrangement gives a free space 
behind the back sheeting for the play of the rammer 
in loading. The height of gallery may be only 
seven feet; its width, according to the foregoing 
arrangements, is four feet. It should be covered on 
top by at least three feet of earth. The level of the 
gallery should be the same as the ditch; and there 
should be a small ditch in front of it, to prevent the 
enemy from closing on the loopholes, or obstructing 
their fire by filling the ditch in front of them by 
means of sand bags, fascines, &c. The entrance 
to the gallery is by a narrow door. 

A scarp gallery, either for musketry, or for one 
or two pieces of cannon, may be constructed to pro¬ 
cure a flank fire in ditches with dead angles. These 
galleries may be made in all respects like a double 
caponniere ; the bottom of the gallery being sunk 
low enough to allow the greater portion of the ditch 
to be swept. As the top of the gallery must sup¬ 
port that portion of the parapet of the work above, it 
must be firmly shored by strong timber. The rear 
of the gallery must be open, and there should also 
be an escape for smoke at the berm of the parapet 
above the gallery. 

A construction of a like character may be used 
to form a blind for one or two guns which it may 
ue particularly desirable to place under cover from 
an enemy’s artillery. The sides of the blind may 
be farther secured by placing against them either 
gabions or sand bags. 






EXPLANATIONS OF PLATE VII. 


Fig. 46. Shows a plan a of a double caponiere, with flanking 
arrangements, the postern b, leading from the main 
work into it; the small ditch c, around it; and an 
abattis d, on the scarp, where it is joined by the 
caponiere. 

Fig. 47. Shows a cross section, a, of a Counterscarp Gallery; an 
exterior elevation, b, of the gallery ; and a cross sec¬ 
tion, c, of a timber revetmen t , formed of a framework 
and thick plank, laid horizontally, behind the up¬ 
rights. 

Fig. 48. Plan of a Redan Line, with a passage, a, in the curtain, 
covered by a small redan. 

Fig. 49. Plan of a Tenaille Line. 

Fig. 50. Plan of a Cr^mailliere Line between two salient priest- 
caps. 

Fig. 51. Plan of a Converging Cr6mailli6re line across a valley. 











































CHAPTER IX. 


LINES OR COMPLEX INTRENCHMENTS. 

193. Dispositions made to cover extended posi¬ 
tions, and which present a front but in one direction 
to the enemy, are termed Lines. There are two 
classes of lines —Continued Lines, and Lines with 
Intervals. Continued lines present no openings 
through which the enemy can penetrate except the 
ordinary outlets. Lines with intervals consist of 
detached works, whicli are enclosed partly, or en¬ 
tirely, throughout their perimeters, arranged in de¬ 
fensive relations with each other; and presenting 
wide intervals between them defended only by their 
fire. 

194. The same general principles apply to lines 
as to other intrenchments ; but, from their great 
extent, they usually receive a slight relief, and the 
simplest angular figures are adopted for their plan. 
In laying them out, the engineer should avail him¬ 
self of all the natural obstacles presented by the 
position, so as to diminish the labor of erecting ar¬ 
tificial ones. 

195. Continued Lines. The simplest arrange¬ 
ment for a continued line, consists in a series of 
redans (Fig. 48) connected by straight curtains; it 
is termed the redan line. The faces of the redans 
are sixty yards in length; their salient angles 60° ; 
and the distance between their capitals one hundred 
and eighty yards. 

196. This combination will place the salients at 
one hundred and sixty yards from the collateral re¬ 
enterings. An inspection of this system shows that 


70 


the ditches are not flanked; tnat the salients are 
not well protected, owing to the cross fire leaving a 
considerable sector without fire in front of them; 
that the curtains, which, from their position, are the 
strongest points, are the best defended, and in turn 
Ihey afford no protection to the faces. All these 
defects become more sensible as the redans are 
placed farther apart. 

197. To remedy the defects of the redan line, it 
has been proposed to break the curtains forward 
(Fig. 49) so as to form two branches, one perpen¬ 
dicular to the face of each redan. This suggestion 
has led to the ienaille line, which consists of a com¬ 
bination of small and large redans, or simply of 
redans of the same size, forming salient and re¬ 
entering angles. This combination is superior to 
the redan line. The salients are protected by a 
cross fire, and the ditches of the large redans are 
partially flanked ; moreover, it presents fewer assail¬ 
able points, on a given front, than the redan line; 
and its retired parts afford good positions for artillery. 

198. The faces of the large redans should not 
exceed one hundred and sixty yards; and their 
salient angle should not be less than 60°. The 
faces of the small redans should not be greater than 
forty yards, and should be perpendicular to those of 
the large redans. These combinations will give 
two limits for the length of the capitals of the large 
redans, and for their distance apart. When the 
salient angles are 60° the length of the capitals will 
be about one hundred and thirty-eight yards, and 
the distance between them two hundred and twenty- 
eight yards. When the salient angle of the small 
redan is 60°, the capitals of the large redans w,ill 
be eighty yards long, and the distance between them 
three hundred and sixteen yards. In the first case 


71 


there will be a greater number of assailable points 
on a given front, but the re-enterings will be the 
stronger; in the second case the reverse of this 
will happen. Of course the size of the redans will 
not be restricted to the limits here laid down. This 
system is defective, in presenting very long faces to 
an enfilade fire, and in taking up a considerable 
depth of ground, from the salients to the re-«enter- 
ings, which restricts its application to particular 
localities. 

199. The indented line (Fig. 50) is principally 
used in place of a straight curtain between two 
advanced works, which are too far apart to protect 
each other and the space between them. 

200. When the ground between the advanced 
works is level, or nearly so, the branches of the 
cremaillere form salient and re-entering angles, 
which are on the same right lines. The long 
branches alternate from the middle point, where 
either a salient or re-entering angle is formed ; the 
latter is preferable, as it is strongest, and may be 
arranged with flanks and a curtain, which will be 
better situated for defence than the two faces form¬ 
ing a salient angle. When there is a valley between 
the two advanced works (Fig. 51), the branches of 
the cremaillere should conform to the slopes of the 
ground; the long branches should be thrown back, 
so that their prolongation shall fall within the 
salients of the advanced works to avoid an enfilad¬ 
ing view of the enemy. The middle point may be 
arranged as in the preceding case. 

2CT1. The cremaillere line is more easily adapted 
to irregular sites, particularly to the sides of hills, 
or similar slopes, than either of the preceding dis¬ 
positions, because it requires but a slight depth of 
ground. 




72 


202. Owing to the imperfect flanking arrange¬ 
ments of the preceding systems, it has been pro¬ 
posed to use bastion lines. They are laid out by 
placing the salients two hundred and fifty yards 
apart, and making the perpendicular of the front 
equal to one sixth. 

203. Another arrangement of the bastion line is 
the one termed with double flanks. (Fig. 52.) The 
salients, in this case, should be between four hun¬ 
dred and five hundred yards apart. The figure ex¬ 
plains itself. By this arrangement there are fewer 
assailable points on the same front; one of the bas¬ 
tions is placed in a strong re-entering; and the 
salients of the advanced bastions are protected by 
the flank fire of the collateral advanced bastion, and 
also of the retired bastion. 

204. The principal objection to the bastion line 
is its great development, and the consequent increase 
of labor and time for its construction. 

205. Continued lines are not suited to an active 
defence ; and this is a grave objection to their use. 
The enemy, if repulsed by their fire, can retreat in 
good order, and renew the assault at a more oppor¬ 
tune moment; because the assailed, if they attempt 
a sortie, must defile through narrow outlets, and 
present a feeble front to the enemy during the ope¬ 
ration of defiling. They are, however, an admira¬ 
ble defence for irregular troops, owing to the confi¬ 
dence which they inspire. They also serve to guard 
against a surprise, and to prevent the predatory ex¬ 
cursions of small detachments of the enemy. 

206. Lines with intervals. The detached works 
used for these lines may be either lunettes or square 
redoubts (Fig. 53) ; their salients are two hundred 
and fifty yards apart, and their salient angles may 
usually be 90°. The faces about sixty yards, and 




73 


the flanks about forty yards, are so arranged as to 
sweep the ground in front of the salients of the col¬ 
lateral works. In the rear of the first line, and 
opposite *o the intervals, redans are placed to flank 
the facet of the first line ; the faces of the redans 
may be about thirty yards. About two hundred 
yards in the rear of the first line, and opposite the 
lunettes, cavalry epaulments are thrown up, to cover 
squadrons of cavalry to act on the flanks of the 
enemy, when his columns are shaken by the fire of 
the works. 

207. The works of the first line are large enough 
to contain from three hundred to four hundred men, 
with a field battery in each, for their defence. The 
redans are good positions for batteries to flank the 
first line. Redoubts present an advantage over lu¬ 
nettes, because they are equally strong throughout, 
but this is accompanied by the defect that their rear 
faces may be used against the assailed if the enemy 
should carry them. The gorges of the lunettes 
should be enclosed by an abattis, palisading, &c., 
which will not afford a shelter to the enemy should 
he get possession of them. 

208. A system of defence has been proposed by 
General Rogniat , former Chief of the French En¬ 
gineer Corps , in his work Considerations sur Vart 
de la Guerre, the spirit of the arrangement of which 
partakes both of the bastion line with double flanks, 
and of the line with intervals. 

209. Points two hundred and fifty yards apart 
are taken for the salients of the lunettes ; their 
faces and flanks are placed in defensive relations; 
and between them a redan, with a pan-coupe, is 
placed to flank the faces, without intercepting the 
fire of the flanks; a straight curtain is carried from 


* 


7 


74 


the redan, and leaves an interval of ten yards be¬ 
tween it and the flanks of the lunettes for sorties. 

210. With regard to the profiles, the lunettes re¬ 
ceive the minimum profile both for the parapet and 
ditch. The redans are simple epaulments to cover 
cannon fired in barbette; and the curtains consist 
of a trench with the earth thrown in front to form 
a parapet, which is so arranged that the infantry 
may march from the trench in order of battle over n. 

211. The advantages claimed for this system 
are, first, the short time required to form the works, 
by which an army may entrench its field of battle 
in one night; second, the lunettes form the first line 
of the order of battle, and contain only infantry, and 
the batteries are placed in the redans, where they 
are more secure, protect the lunettes, and withdraw 
the fire of the enemy’s artillery from the lunettes; 
third, the curtains are defended by infantry, who 
can sally from them at a moment’s warning, and 
aided by the light artillery and cavalry, who de- 
bouche through the intervals between the curtains 
and lunettes, and attack the enemy in flank. If the 
flanks of his position are not secured by natural ob¬ 
stacles, Gen. Rogniat proposes to throw up a strong 
square redoubt on each flank, and to place a heavy 
battery in the interval between the redoubt and the 
adjacent lunette. 

212. Lines with intervals are peculiarly adapted 
to well disciplined and active troops. The works 
thrown in advance constitute the first line of the 
order of battle, against which the first shock of the 
enemy is partially thrown away, and he dare not 
attempt to neglect them, for an endeavor to penetrate 
through the intervals would expose his flanks to a 
close and deadly cross fire. If the enemy is re¬ 
pulsed, the main body of the army, which is drawn 





75 


up in rear of the u orks, immediately assumes the 
offensive, and, by a vigorous advance movement, 
charges the enemy in turn, relying on the works 
to cover its retreat if driven back. 

213. In every combination of this nature the 
flanks are the weak points ; they should rest, if 
practicable, on some unassailable point, as a marsh, 
river, &c. ; otherwise very strong works should be 
thrown up for their protection. 

214. It has been proposed, by some writers, to 
throw up several lines of detached works for the 
defence of a position; so that the troops in the first 
line may retreat under cover of the second, and so 
on. This arrangement, in the first place, can seldom 
be made, without weakening the order of battle , and 
therefore weakening the defence, by too great a dis¬ 
semination of the troops. Moreover, in works of 
great extent there never can be that concert, which 
is so essential to a vigorous defence, from the im¬ 
practicability to direct it properly. The troops, 
destined to act offensively against the enemy if 
repulsed, are too far in the rear to be brought up in 
time ; and the ground being greatly cut up, by such 
a multiplication of works, will render the manoeu¬ 
vres slow and difficult. Besides, a very capital 
objection in war , the time and labor required to throw 
up so many works are altogether beyond what can 
be disposed of in the ordinary circumstances of an 
army. 


CHAPTER X. 


THE ADAPTATION OF INTRENCHMENTS 10 PARTICU 
LAR LOCALITIES. 

215. The object of this chapter is to lay down 
some general rules respecting the manner of com¬ 
bining artificial and natural obstacles, so as to draw 
the greatest resources from both in strengthening a 
position. 

216. Mountainous sites. The crests, and gorges, 
are the most important military features of a moun¬ 
tainous position. It is through the latter that the 
roads are made, and the former, from their elevation, 
command the latter. The crests should therefore 
never be abandoned to the enemy, although from 
their position, or distance, they may not directly 
overlook the gorges; for, independently of the real 
advantage of position, which the enemy would thus 
acquire, he would possess a relative advantage in 
the moral effect produced on troops when they find 
themselves in a commanded position. 

217. If the base of the mountain does not stretch 
out too far from the summit to admit of a sure re¬ 
treat on the latter, works may be thrown up for the 
defence of the base, with intermediate works be¬ 
tween the base and the summit placed on the 
secondary ridges, or other commanding points. 
But if the distance between the summit and 
base is ^?at, and particularly, if it is decided be¬ 
forehand to retreat upon the summits, in case of 
disaster, then the base should be disregarded. 

218. The works thrown up for the defence of the 
summit s'.ould be laid out on the brow of the height, 






EXPLANATIONS OF PLATE VIII. 


Fig. 52. Plan of a Bastion Line with double flanks. 

Fig. 53. Plan of a Line with Intervals of lunettes, or square re¬ 
doubts, flanked by retired redans ; with cavalry epaul- 
ments in rear. 

Fig. 54. Shows the plan and profiles of General Rogniat’s 
Line. 

























































































11 



for the purpose of overlooking and guarding its 
sides. In planning the works, the re-entering parts 
of the brow should be arranged to obtain a cross 
and flank tire on the slopes in front of the salient 
points; and particular regard should be had to the 
inclination of the slopes, 411 arranging the relief and 
the means of defence. 

219. Very steep slopes will not admit of a de¬ 
fence with artillery, because the gun cannot be tired 
under a greater depression than one-sixth, and 
unless the shot take effect the enemy will be in¬ 
spirited to advance, confiding in the safety of his 
position. In slopes of this character the works 
may consist simply of a parapet (Fig. 55), in the 
form of a glacis, without any ditch, the earth for 
the parapet being taken from an interior trench; in 
some cases a dry stone wall may be substituted for 
an earthen parapet. An abattis may be formed in 
front of the parapet within close musket range ; 
and heavy round logs, or large masses of rock, be 
arranged along the parapet, ready to be rolled over 
on the enemy should he break through the abattis. 
Steep escarpments of rock are generally considered 
inaccessible; but those points should.never be left 
to their own strength. It is always prudent to post 
a small detachment to frustrate an attempt of the 
enemy to surprise them. 

220. A steep natural slope (Figs. 56, 57) may 
be readily made inaccessible by cutting away the 
face of the eminence. 

221 . It may, in some cases, be indispensably ne*- 
cessary to guard certain points at the base of a 
mountain, is, for example, where the base is washed 
bv a river, over which there is an important ferry, 
llnder such circumstances the point to be guarded 

should be protected by a strong work; and a chaii? 

7* 



78 


of posts, placed on the most commanding points 
between the summit and the base, should connect 
the two. These posts should, when practicable, be 
placed in defensive relations, and in all cases their 
fire should sweep all the ground between the two 
principal points. The interior of the posts most 
advanced, should be exposed to the fire of those in 
their rear, in order that the enemy may be driven 
out, should he succeed in forcing his way into any 
one. As these posts will require a considerable de¬ 
tachment for their defence, care should be taken 
not to multiply their number unnecessarily, and 
never at the expense of the main defence. 

222. All communications, leading through the 
mountains, should be carefully guarded, both at 
their outlets and at the most suitable intermediate 
points for defence ; otherwise the most respectable 
positions will be liable to be turned by the enemy. 
If the communications are not of use to the assailed, 
they may be barred by a line of abattis, or by an 
artificial inundation, &c. ; and they should be watch¬ 
ed by a detachment of light troops, whose retreat 
on the main.works should be secured in case of an 
attack by superior forces. 

223. If the communications are of use to the 
assailed they should be defended by intrenchments, 
which should command and enfilade them in the 
most effectual manner. 

224. Forests. An abattis is the natural in- 
trenchment of forests. The position of the abattis 
will depend on circumstances. If light troops are 
in observation in advance of the forest, they may 
be covered by a line of abattis, to prevent a sur¬ 
prise, and to enable the corps, if driven back, to 
retire under cover of the forest. Other lines of 
abattis may be formed at suitable point* in the 


79 


forest itself. If the forest is in front of intrench* 
inents, the trees must be felled within cannon range, 
and an abattis be formed. 

225. Marshes. An impassable marsh, or bog, 
may serve to render a weak point unassailable, if 
the enemy can neither flank nor turn it. Like all 
points secured by natural obstacles, it should be 
vigilantly guarded to frustrate any attempt to cross 
it by surprise. 

226. Rivers. The works planned for the defence 
of a river will depend on the object to be attained, 
whether it be simply to prevent the enemy from 
crossing, or to give the assailed the means of a secure 
communication with the opposite shore. 

227. The points most favorable to the passage ot 
the enemy are fords ; and when the river is not 
fordable, the points where an elbow is formed, the 
re-entering being towards the enemy. To guard 
these weak points, works should be placed in a 
suitable position to prevent the enemy from ap¬ 
proaching the opposite bank ; and in the case of a 
ford, the plan of the works (Fig. 58) should be so 
arranged that their fire can be concentrated on the 
ford ; and, if the assailed have cavalry, a free space 
should be left between the water and the works for 
the cavalry to act on; the object being to charge 
the enemy whilst in disorder from crossing the ford. 

228. To keep open a free communication with 
the opposite shore, it will he necessary to throw up 
works there, of sufficient strength to allow the 
assailed time to effect a safe retreat, should they be 
attacked by superior forces. As these works serve 
to cover the bridges in their rear, they are termed 
letes-de-pont, or bridge-heads. The best points to 
erect a bridge-head are the bends, or elbows of the 
river, the re-entering being towards the assailed. 


80 


The reasons for selecting these points are, that the 
bridge-head may be protected by a good flank and 
cross fire from the opposite shore, which from its 
shape is most favorable for this purpose; secondly, 
from the manner in which elbows are formed, the 
point occupied by the bridge-head will commonly 
be commanded by the opposite shore, and should the 
enemy succeed in obtaining possession of the bridge¬ 
head, he will have all the disadvantages of a com¬ 
manded position; thirdly, the elbow is not only 
unfavorable to the enemy, by preventing him from 
placing a battery in a position to destroy the bridge, 
but it also may prevent floating bodies, thrown into 
the current by the enemy with the same view, either 
by their shock, or by fire, from coming directly in 
contact with the bridge, as the chances are, that 
those bodies will strike one or the other shore before 
reaching the bend. 

229 The plan of a bridge-head should be care¬ 
fully studied on the ground; and it should, as far as 
practicable, satisfy the following conditions. 

1st. Admit of a defence until all the troops have 
effected a safe passage. 

2d. Cover the bridge from the enemy’s artillery; 
so that the retreat may not be cut off'by the destruc¬ 
tion of the bridge. 

3d. Be suited to the end in view ; if, for example, 
its object is to afford the means to small detachments 
of making incursions on the opposite shore, a small 
unimportant work will be all that is required ; but if 
a large corps is to pass, either in retreat, or to act 
offensively, then the works should be arranged with 
wide intervals, to allow the troops to debouche in 
mass, and display readily in order of battle. 

4th. The flanks of the works should rest upon 
the banks,to prevent their being turned; and,when 


81 


practicable, they should be protected by flanking 
arrangements from the opposite shore. 

5th. A strong interior redoubt should secure* the 
bridge against an attempt on the part of the enemy 
to obtain possession of it by storming the works. 

230. The practicability of obtaining flanking ar¬ 
rangements from the opposite shore will materially 
affect the plan of the bridge-head. If the breadth 
of the river is over one hundred yards, not much 
reliance can be placed on a flanking arrangement 
for musketry ; and if the breadth is from six hun¬ 
dred to eight hundred yards, it will still admit of a 
very effective flank fire of artillery, but not greatly 
beyond this. For an unimportant work, therefore, 
which can be flanked by musketry from the opposite 
shore, a redan or a lunette will be a very suitable 
form ; and if the work can only be flanked by can¬ 
non, a priest-cap (Fig. 59), or a redan, with crotchets , 
or flanks, near the extremities of the faces, and per¬ 
pendicular to them, arranged for musketry, will be 
a very suitable form. Neither of these w T orks, how¬ 
ever, admits of sufficient strength to cover a very 
important point, whose loss might compromise the 
safety of an army, or the success of a campaign. 
The best arrangement for this purpose is either a 
simple or a complex crown. 

231. The simple crown (Fig. 60) consists of a 
central bastion, and two half bastions near the banks. 
In planning this work, the flanks which protect the 
central bastion should be longer than the other two, 
as it is hardly probable that the enemy will attempt 
an attack on any other point but the salient. The 
batteries on the opposite shore should sweep the 
ground immediately in front of the faces, and cross 
their fire in advance of the salient. 

232. The complex crown-work co: 6ists of a po- 


82 


{ygon of three or more sides, on each o which a 
bastion front is constructed. 

283. If the bridge-head is to cover the manoeu¬ 
vres of a large army, either advancing or retreating, 
a strong simple crown (Fig. 60), with a system of 
detached lunettes, about six hundred yards in front 
of it, presents a very suitable arrangement. The 
lunettes may be arranged as in the system of Gene¬ 
ral R< gniat. The central bastion of the crown- 
work should be armed with a strong battery of heavy 
guns to protect the lunettes; and heavy batteries, 
on the opposite shore, should sweep the ground be¬ 
tween the lunettes and crown-work. 

234. If there are islands in the river near the 
works, they may be fortified with advantage to flank 
them. 

235. Besides the arrangements already mentioned, 
intervals of from ten to twenty yards should be left 
between the shore and the works, for the troops to 
defile through ; the interior of the work is covered 
by a traverse in rear of the interval. A small de¬ 
fensive stoccade should be formed immediately at 
the head of each bridge, to enable a company of 
picked men to defend it until the bridge can be cast 
loose from the shore. 

236. An interval of at least one hundred yards 
should be left between the bridges, if more than one 
is used, and about the same distance should be left 
between each bridge and the wings of the work. 

237. Villages. A village may play a very im 
portant part in an action, if suitable arrangements 
are made for placing it in a defensive attitude, to 
prevent the enemy from carrying it by storm. If 
the village is not too far in front of the line of bat¬ 
tle, it should be strongly occupied ; its rear being 
left open to receive succors. But if, by occupying 


83 


the village, a very salient, and therefore a very weak 
point, would be presented to the enemy, then it 
would be best to demolish it; to prevent the enemy 
from taking advantage of it, to cover his manoeu¬ 
vres whilst advancing, or from throwing a detach¬ 
ment into it, to cover his retreat if repulsed. 

238. To admit of a good defence, the houses of 
the village should be built of brick or stone, and not 
be too scattered. The enclosures of the gardens 
should consist of brick, stone, or mud walls, or a 
thick-set hedge. Wooden villages do not admit of 
a good defence, on account of the ease with which 
they may be burnt; but they should not on this ac¬ 
count be abandoned to the enemy; for they offer a 
shelter, if only a temporary one, to troops, and by 
checking the enemy only for a short time, may ren¬ 
der important service. Villages consisting of log- 
houses are the most defensible. 

239. Military Posts. The term military post is 
applied to isolated positions, occupied by small de¬ 
tachments, for the purpose of guarding particular 
points which are of importance during the opera¬ 
tions of a campaign, or for a longer or shorter pe¬ 
riod. These positions are frequently villages, farm¬ 
houses, &c. 

240. The officer charged with placing a village 
in a defensive attitude, should first proceed to a 
careful examination of its environs, for the purpose 
of ascertaining what natural obstacles, and what 
facilities, they present to the approach of the enemy. 
Very slight accidents of ground may be greatly im¬ 
proved by trenches of trifling depth, with a profile 
similar to Fig. 55, to place troops speedily under 
cover. When the surface is undulating it should 
be particularly examined with this view, the officer 
taking a position at different points and directing 


84 


men to approach him, and occasionally stooping to 
observe how much they will be masked from a fire 
at various heights above the surface. The side 
slope of a ridge from the enemy will be the best po¬ 
sition for the trench to obtain speedy cover, provided 
the ground in advance of it can be well swept from 
its crest. The next points to be considered are the 
walls, hedges, &c., of enclosures, which may be 
turned to a useful account for the defence, or which 
might serve as a shelter to the enemy. After hav¬ 
ing finished this examination, he will next proceed 
to lay out his works ; arranging their plan so as to 
draw every possible advantage from the natural and 
artificial obstacles at hand, to render certain points 
inaccessible, and to procure a shelter for his troops, 
and flanking arrangements by means of the walls, 
hedges, &c. If there should be danger of an at¬ 
tack before these works can be completed, the roads 
leading to the village, by which the enemy might 
approach, should be broken up ; and cannon should 
be placed in the best position to guard the most ac¬ 
cessible points. The streets of the village should 
be barricaded, and the houses and walls, in the 
vicinity of the barricades, should be placed in a de¬ 
fensive attitude. In taking these preparatory mea¬ 
sures against a sudden attack, any means that will 
afford the troops a cover from the enemy’s fire should 
be resorted to; bales of cotton, or wool, casks set 
side by side, and filled with earth, piles of timber, 
&c., have been used with great success under such 
circumstances. As the various arrangements called 
for under such circumstances will demand great 
activity on the part of the garrison, care should be 
taken to distribute the work among the most con¬ 
versant with it, placing the men who have any 
skill in the handling of tools at preparing the wooeen 


85 


and stone defences, and common laborers at throw- 
ing up the earthen works, &c. 

241. The works that surround the village should 
be placed so far from the houses that the troops 
shall not be incommoded either by the splinters oc¬ 
casioned by the enemy’s artillery, or by the flames 
and smoke, should the houses be set on fire. The 
communications from all the exterior defences to 
some central rallying point should be carefully ar¬ 
ranged, to avoid confusion in retreat, and check the 
pursuit of the enemy. The garrison should be 
made perfectly familiar with them, and with the re¬ 
sources they may afford, in case of need. Short¬ 
cuts should be made for this purpose by breaking 
through garden walls, the party walls of houses, 
&.C., and by the erection of barricades at all suitable 
points to make a stand. 

242. Hedges. A thin-set hedge cannot be placed 
in a good state of defence, and should therefore be 
destroyed, to prevent its interfering in any manner 
with the defence. A thick-set hedge (Fig. 61), if 
over six-and-a-half feet high, should be cut down to 
this height, and the cuttings be set into the hedge 
to render it less penetrable; a small ditch is dug 
in front of the hedge, the earth from which serves 
to form a banquette and a slight parapet, which are 
thrown up against the hedge. If the hedge is less 
than six-and-a-half feet high (Fig. 62), it is cut 
down to the height of four-and-a-quarter feet ; a 
ditch or trench, about three feet wide at bottom, and 
two feet deep, is dug behind the hedge, and the 
earth is thrown up against it, as in the last ease. 
A width of two or three feet should be left between 
the trench and the earth thrown against the hedge to 
serve as a banquette. 

243. A simple ditch behind a hedge will often 

8 


86 


serve as a good cover for light troops without any 
other preparation. 

244. Walls. If a wall is of brick, or stone ma¬ 
sonry, or of mud, and at least six-and-a-half feet 
high, it may be arranged for defence by cutting 
loopholes through it, at three feet apart. For walls 
two feet thick, the interior width of the loopholes 
should be fifteen inches, the exterior width four 
inches, and the interior height twelve inches, and 
the exterior should be arranged to allow the fire to 
sweep as great a space as practicable. The bottom 
of the loop-hole is four-and-a-quarter feet above the 
ground. A small ditch, about three feet in depth, 
should be dug on the outside of the wall, and the 
earth thrown against it, to prevent the enemy from 
closing on the loopholes. 

245. If the wall is less than six-and-a-half feet 
high (Fig. 64), it should be cut down to the height 
of four-and-a-quarter feet; or else a banquette should 
be made against it. A trench is dug behind it, as 
in the case of a hedge of the same height; a ditch 
of about two feet deep should be dug in front of the 
wall, to prevent the enemy from reaching the as¬ 
sailed with the bayonet, and to place an obstacle tc 
his climbing over the wall. 

246. Walls which are eight feet high (Fig. 65), 
may be arranged with a double tier of fire ; for 
this purpose a banquette of boards, sustained by 
trestles , or by casks, is made, to enable the assailed 
to fire over the wall; loop-holes are made near the 
foot of the wall, and a ditch is dug behind it, to 
obtain a second tier of fire. In this case no ditch 
should be made on the outside of the wall, because 
it might enable the enemy to close on the loop¬ 
holes. 

247. If a long line of wall should require flank- 







EXPLANATIONS OF PLATE IX. 

Fig. 55 Shows the Profile on a hill side where the terre-plein is 
excavated behir d the parapet. 

Fig. 56. Shows a similar c ise to Fig. 55 ; the natural face of the 
hill is cut into steps to prevent the embankment from 
sliding. 

Fig. 57. Shows a Profile of an Escarped hill side. 

Fig. 58. Shows the plan of a work to dispute the passage of a 
ford. 

Fig. 59. Shows the plan of a T6te-de-Pont, composed of a Priest- 
Cap, a, with flanks, or crotchets; and flanking bat¬ 
teries, c, on the opposite shore. 

Fig. 60. Shows the plan of a T6te-de-Pont, composed of a simple 
Crown, a ; a system of advanced lunettes, d ; and a 
flanking arrangement of batteries, at d and c, on the 
island, and opposite shore. 

Figs. 61 and 62. Show Profiles of a Defensive Hedge 

Figs. 63 and 64. Show Profiles of Defensive Walls. 




































































87 


ing arrangement, a timber work, termed a iam- 
hour, is made on the outside ; this work is made 
like a defensive stoccade, with square or round tim¬ 
ber about six or eight inches in thickness ; the plan 
of the tambour is that of a redan with a salient 
angle of 60°. A hole is made through the wall 
to communicate with the tambour, and loopholes 
are made in the wall to flank the faces of the 
tambour. 

248. Barricades. Wagons, or carts, sunk in the 
ground up to their axle-trees, and loaded with stones, 
or earth, will form a very good barricade. A pile 
of loose stones will serve the same purpose in some 
cases ; also timber laid in piles, lengthwise and 
crosswise, with the open spaces filled with stones, 
or earth, forms an excellent barricade. 

249. Barricades should be defended from behind 
with musketry, and cannon loaded with case shot: 
a work, like a defensive stoccade, will therefore b< 
the best arrangement for them. 

Houses . To place a house in a defensive atti¬ 
tude, the doors and windows of the lowest story 
should be firmly barricaded, and loopholes be made 
as in the case of a wall. A tambour should be 
placed before the doors, both for their protection 
and to procure flanking arrangements if required. 
The windows of the upper stories should be partly 
barricaded, to cover the troops within, and loopholes 
should be arranged as in the lower stories. 

250. The roof, if not fire proof, should be torn 
down, and the floor of the upper story be covered 
with earth or dung, moist from the stable, to the 
depth of about two feet. 

251. If it is intended to defend the upper stories, 
should the enemy succeed in forcing the lower, the 
stairs should be torn down, and slight ladders be 


88 


used in their stead; holes should be made through 
the floor to fire on the enemy in the lower story, or 
to throw heavy articles, or boiling water, &c., on 
him. 

252. If there are balconies to the windows of the 
upper stories, or an upper gallery, they can readily 
be placed in a defensive state by placing thick boards 
as a shelter on the outside, and cutting holes through 
the floor to defend the doors and windows of the 
low T er story. 

253. If there are no conveniences of this nature, 
a temporary structure, termed a machicoulis gallery 
(Fig. 67), may be formed, by placing stout pieces 
of scantling through holes made in the wall, on a 
level with the floor; these pieces being confined to 
the floor on the inside, either by nailing them to it 
or by tying them with rope to the joists; they should 
project from three to four feet beyond the wall on 
the exterior, and vertical pieces of smaller scantling, 
about four feet long, should be nailed to them, on 
which boards are nailed to cover the troops from the 
enemy’s fire; these boards should be at least three 
inches thick. The flooring of the gallery is laid 
on the horizontal pieces, and holes are made through 
it to fire on the enemy, or to throw grenades, stones, 
&c., on him. 

254. Any similar arrangement which will shelter 
a man, in the act of firing from a window on the 
foot of the wall, or in throwing over stones, &c., 
will serve the same purpose as a machicoulis galle¬ 
ry. A table might easily be arranged to answer the 
end in view. 

255. In arranging a house for defense, everything 
should be turned to account. The chimneys may 
be partly torn down on the interior to obtain bricks 
to barricade the windows. The flooring boards may 


89 


be used for the same j urpose, and pillows, blankets, 
books, &c., be thrust in between the boards nailed 
on the inside and outside of the windows. By 
tearing away some of the partitions, and taking up 
some of the joists of floors, heavy timber may be 
procured for the machicoulis galleries, for buttress¬ 
es, for the lower barricades, for shores, &c. 

256. The intelligence of the officer will readily 
suggest to him the uses to which the objects at 
hand may be applied. 

257. Positions and Intrenched Camps. There is 
no talent more essential to an officer than that of 
seizing at a glance the strong and weak points of a 
position. This talent, known by the name of the 
Military coup d'ccil, can be acquired alone by prac¬ 
tice and study ; for whatever may be said of natu¬ 
ral gifts, no apprehension, however quick it may be, 
can supply the places of these indispensable requi¬ 
sites in every art, and in no one are they more so 
than in the Military Art. 

258. Positions derive their great importance from 
the influence of fire-arms in the decision of battles; 
for whatever enables one party to deliver its fire 
with effect against the other, whilst it, at the same 
time, remains sheltered in any degree from that of 
its adversary, places the advantage, all other things 
being equal, greatly on its side; and it is this ad¬ 
vantage which should be principally kept in view 
in selecting a position. 

259. Woods, commanding heights, precipices, 
and villages, constitute the strong points of a po¬ 
sition. They serve as points of support against 
which the wings of the army rest; or else, by cover¬ 
ing parts of the front, they serve as the key points 
in the defence. 

260. A wood, if properly intrenched, covers the 

s* 


90 


Infantry from the attacks ot cavalry; conceals its 
manoeuvres, and enatles it to deliver its fire without 
being exposed to that of the enemy. 

261. Heights, by giving a commanding view of 
the su r rounding ground, increase both the range 
and the effects of fire-arms; whilst they, at the same 
time, serve to screen the troops behind them until 
they are required to be brought into action. Pre¬ 
cipices otier similar advantages to heights, and are 
moreover unassailable. 

262. v illages serve as secure shelters for detach¬ 
ments, wtiich, by their fire, cover the manoeuvres 
of the troops in their rear; and, if properly in- 
trencheu, will cause the enemy great loss in his 
effort to force his way into them. 

263. Rivers, marshes, hollows, and ravines, are 
the most unfavoraD.fe features of a position, because 
they prevent a free circulation from one point to 
another, and thus impede the manoeuvres ; and they 
are exposed to the full fire of the enemy. They 
may however be of service when they are so placed 
as to support the wings. 

264. The best positions are those which, being 
in due proportion to the force by which they are 
occupied, command all the surrounding ground 
within cannon range, the ground descending in a 
gentle slope to the front, presenting woods, villages, 
&c., to support the wings, and cover parts of the 
front, and admitting of a free circulation from one 
point to another, with secure communications in 
their rear in case of retreat. If with these advan¬ 
tages, they present marshes, or other obstacles, 
which will embarrass the enemy’s movements, 
and force him to advance in column, exposed to 
die fire and free manoeuvres of the assailed, they 


t 


91 


will unite everything' desirable in a favorable field 
of battle. 

265. Troops should always be encamped in order 
of battle, to avoid the consequences of a surprise. 
When a camp is fortified, it is termed an intrenched 
camp. The same rules and general principles ap¬ 
ply to the choice of a site for a camp, and the manner 
of fortifying it, as to other positions. These rules 
and principles have been so fully developed in the 
preceding part of this work, that there remains 
nothing more to be said here which would not be a 
repetition of what has already been laid down. 


* 


I 


CHAPTER XI. 

ATTACK AND DEFENCE OF IIITRENCHMENT8. 

266. Attack. The subject of the attack admits 
of two natural divisions ; the first of which compre¬ 
hends all the preliminary steps taken before the 
troops are brought into action; the second all the 
subsequent operations of the troops. 

267. An attack is made either by surprise, or 
openly. In both cases exact information should be 
obtained of the approaches to the works; their 
strength; the number and character of the garri¬ 
son ; and also the character of the commander. 
This information may be obtained through spies, 
deserters, prisoners, and others who have access to 
the works ; but implicit faith ought not to be placed 
in the relations of such persons, as they may be in 
the interests of the garrison ; and in all cases they 
should be strictly cross-examined and their differ¬ 
ent representations be carefully compared with each 
other. 

268. The best source of information is an ex¬ 
amination, or reconnaissance, made by one or more 
intelligent officers. This reconnaissance should, if 
possible, be made secretly; but as this will not be 
practicable if the garrison show even ordinary 
vigilance, it will be necessary to protect the recon¬ 
noitring officer by small detachments, who drive 
in the outposts of the garrison. The object to be 
attained by the reconnaissance is an accurate 
knowledge of the natural features of the ground 

* exterior to the works; the obstacles it presents, and 
the shelters it affords to troops advancing; the 


93 


obstacles in front of the counterscarp and in the 
ditches ; the weak and strong points of the works, 
and the interior arrangements for the defence. If 
the work is an isolated post, information should be 
obtained as to the probability of its being succored 
in case of an attack; the length of time it must 
hold or to receive succor; and the means it 
possessea of holding out. 

269. Attack, by surprise. A surprise is an un¬ 
expected attack , for which the assailed are not 
prepared. It is, perhaps, the best method of assail¬ 
ing an undisciplined and careless garrison, for its 
suddenness will disconcert and cause irremediable 
confusion. 

270. Secresy is the soul of an enterprise of this 
nature. To ensure it, the garrison, if aware of the 
presence of the troops, should be deceived and 
lulled into security by false manceuvres. The troops 
that form the expedition should be kept in profound 
ignorance of its object until they are all assembled 
at the point from which they are to proceed to the 
attack. 

271. The winter season is the most favorable 
for a surprise, which should be made about two 
hours before day, as this is the moment when the 
sentries are generally least vigilant, and the garrison 
is in profound sleep ; and the attempt, if at first suc¬ 
cessful, will be facilitated by the approach of day, 
and if unsuccessful, the troops can withdraw with 
safety under the obscurity of night. Should there 
be danger, from succors arriving in a short time, the 
attack should be made soon after midnight, when 
the garrison is asleep, so that the troops may retire 
before daylight, after having attained their object. 

272. As a general rule, the troops for the attack 
should consist of a storming pi:.?*y, divided into an 


94 


advanced party and its support, and be followed by 
a reserve of picked men. The advance of the 
storming party will open the way, and be closely 
followed by the support in the assault of the parapet 
and a reserve of picked men. There should be two 
guides,, one in front of the storming party, with the 
detachment of workmen under the command of an 
engineer officer; the other in the rear, under charge 
of a guard, to supply the place of the first, if killed. 
The workmen should be furnished with axes, crow¬ 
bars, pick-axes, &c., and several bags of powder, of 
about thirty pounds each, to be attached to palisad- 
ings, fraises and barriers, to blow them down, if the 
alarm should be given whilst they are opening a 
way through them by other means. All the opera¬ 
tions should be carried on with despatch and in 
silence. Should the sentries challenge, they must 
be secured or bayoneted. 

273. Circumstances alone can determine whether 
it will be advisable to make false attacks with the 
true one. They will distract the attention of the 
garrison, if the alarm is given, from the true attack; 
and a false attack has sometimes succeeded when 
the true one has failed. When made, one should 
be directed against the strongest point of the work; 
as the strong points are usually guarded with less 
vigilance than the others ; and they should all be 
made at some distance from the true attack; and 
orders be given to the detachments making them to 
proceed to the point of the true attack, should they 
succeed in making their way into the work. 

If the attack succeeds, immediate measures 
should be taken to place the works in a state of 
defence, if the position is to be maintained; or else 
they should be destroyed, as far as practicable, 
before retreating from them. 


95 


274. Attack by Open Force. The general arrange¬ 
ments for an open assault, comprehend the opera¬ 
tions to gain possession of the works ; the measures 
for maintaining possession of them, and following 
up the first advantage; and, finally, the precautions 
to be observed in the event of a repulse. 

275. An open assault may be made either with 
the bayonet alone, or with the combined action of 
artillery and the bayonet. The first is the most ex¬ 
peditious method, but it is attended with great 
destruction of life; it should therefore only be re¬ 
sorted to against works of a weak character, which 
are feebly guarded ; or against isolated posts within 
reach of speedy succor. When tried it will usually 
be best to make the attack just before day. If it is 
made by daylight it will, in most cases, be well to 
scour the environs with a few squadrons of cavalry, 
to pick up patroles and stragglers who might give 
the alarm, and then push forward rapidly the as¬ 
saulting columns. If the assailed seem prepared, 
light troops should precede the columns of attack, 
with orders to display in front of the counterscarp, 
and open a brisk fire on the assailed, for the purpose 
of diverting their attention from the columns of 
attack. 

276. In an attack with artillery, the troops are 
drawn up in a sheltered position, or beyond the 
range of the guns of the assailed; batteries are 
then established within about six hundred yards of 
the works, in the most favorable positions to enfi¬ 
lade the faces, and destroy all visible obstacles. 
The batteries keep up an incessant fire of ball and 
hollow projectiles, in order to dismount the cannon, 
and create confusion among the assailed. When 
the fire of the works is silenced, the troops are 
brought forward, and demonstrations are made on 



96 


several points, to divert the attention of the assailed 
from the true point of attack, and prevent him from 
concentrating his strength on that point. Several 
false attacks should be made at the same moment 
with the real one, and each of them should be suffi¬ 
ciently formidable, in point of numbers, to enable 
the troops to profit by any success they may obtain. 

277. The number and disposition of the troops 
making the assault will depend, in so great a de¬ 
gree, on local circumstances, and the arrangements 
of the assailed, that nothing more can be laid down 
under this head than some general rules. 

278. The attack should be led by a storming 
party, composed of picked troops, or of volunteers 
for the occasion ; this party is preceded by a de¬ 
tachment of engineer troops, provided with the 
necessary means to make their way through all 
obstacles, to enable the storming party to assault 
with the bayonet. If the detachment is arrested at 
the crest of the counterscarp, by obstacles which 
must be destroyed before farther progress can be 
made, the leading files of the storming party mav 
open a fire on the assailed to divert their fire from 
the workmen ; but this operation should only be re¬ 
sorted to from necessity, as it breaks in on that unity 
so essential in an operation of this character, and 
impairs the confidence of the soldier in the bayonet, 
on which his sole reliance, in such cases, should be 
placed. 

279. The storming party should be provided with 
light scaling ladders, planks, fascines, strong hur¬ 
dles, &c., for the purpose of descending into the 
ditch ; to mount the scarp; to cover trous-de-loup, 
small pickets, &c., &c. 

280. Another detachment of engineer troops fol¬ 
lows in the reai of the storming party; its duties 


97 


consist in rendering the passages, opened by the 
first detachment, more accessible to the troops, who 
immediately follow it to sustain the storming party. 
This second detachment is also charged with the 
care of placing the work from which the assailed 
has been driven in a defensive attitude, in order to 
frustrate his attempt to repossess himself of it. 
The first detachment should be charged with this 
duty: for, independently of having handsomely ac¬ 
quitted itself in bearing the brunt of the action, it 
may be required to precede the storming party in 
the pursuit of the assailed to his interior works. 

281. The troops destined to support and, if ne¬ 
cessary, reinforce the storming party, advance in 
one or two lines, with cavalry, and some pieces of 
artillery on the wings, to repel sorties. The re¬ 
mainder of the troops follow in order of battle, to 
improve the first successes, or to cover the retreat of 
the assaulting columns, if repulsed. 

282. The salients are generally the points on 
which the storming party advances, unless some 
natural feature of the ground should present 
greater facilities for advancing on a re-entering, or 
in front of a face. When the ditch is gained, 
shelter is sought in a dead angle; and if the work 
is fraised, or resolutely defended with the bayonet, 
a breach must be made, either by firing beforehand 
hollow loaded projectiles into the parapet, or by un¬ 
dermining the scarp with the pick. If the intrench- 
ments consist of detached lunettes, an attack should 
be made on their gorge at the same moment with 
the one in front. 

283. When the assailed are driven from their 
main works, the storming party should press hotly 
on their rear, and endeavor to enter pell-mell with 
them into their interior works, leaving to the troops 

9 


98 


which follow them the care of retaining possession 
of the works gained ; but, if the intrenchments are 
supported by other troops drawn up in order of 
battle, the storming party should halt in the works 
until it is reinforced hy the troops in its rear. 

284. There is no danger to be apprehended, in 
case of a retreat, after an unsuccessful attack on 
an isolated work. But in an attack on intrench¬ 
ments, supported by an army, the retreat of the 
storming party should be covered by cavalry and 
artillery, until it can find safety behind the main 
body of the troops, daawn up in order of battle to 
protect it, and to receive the assault of the assailed, 
should he attempt offensive operations. 

285. In conducting the attack, preparations 
should be made beforehand for removing all the 
artificial obstacles that the assailed may have placed 
before their works, to impede the progress of the 
storming party. This duty is usually intrusted to 
the detachment of engineer troops, who are pro¬ 
vided with axes, picks, and other suitable tools for 
this purpose. When the obstacles are of a nature 
to be easily destroyed by artillery, it should always 
be resorted to. Abattis, palisades, fraises, and en¬ 
tanglements, when exposed, may be readily torn to 
pieces by opening an enfilading ricochet fire on 
them. When cannon cannot be brought to bear 
on these obstacles, an abattis may sometimes be 
set fire to, and palisades, &c., be blown in by 
attaching bags of powder to them. Trous-de-loup 
may be passed, either by covering them with plank 
or strong hurdles, or else by directing the men to 
pass cautiously between them in extended order; 
small pickets may be broken down, or else fascines 
may be spread over them so as to form a tolerably 


99 


stable road-way; fascines may also be used to 
cover the points of spikes. 

286. The passage of the ditch, and the assault 
of the parapet, are the most difficult operations. 
If the ditch is not more than six feet deep, it can 
be leapt into without danger, and the men can 
mount the scarp readily with a very little assistance 
from each other. When the width is not greater 
than twelve feet, the ditch may be crossed by laying 
thick plank, or small scantling, over it. When the 
depth is over six feet, the storming party is usually 
provided, either with small scaling ladders, or with 
fascines, sand-bags, or other means, to fill the ditch 
partly up ; or if these means cannot be procured, 
the detachment dig away the counterscarp into 
steps, throwing the earth into the ditch, and thus, 
in a short time, form an easy entrance to it. Wet 
ditches may be filled up either with sand-bags alone, 
or more expeditiously by attaching sand-bags to 
large fascines, or to trusses of hay or straw. 

287. The assault of the parapet is made by the 
aid of scaling ladders, or by effecting a breach, by 
firing loaded hollow projectiles into the scarp and 
parapet, which, by their explosion, crumble the 
earth down, so as to form an accessible ramp; or 
else the foot of the scarp is undermined with the 
pick, and the mass of the parapet tumbled into 
the ditch. 

288. Defence. The essential point in the defence 
is to have every part of the works guarded by a 
sufficient number of troops to resist an attack on 
all sides. This is of importance not only in iso¬ 
lated works, which can be surrounded, but also in 
continued hues; for although the enemy will 
usually make an attempt to enter only at a few 


100 


points, still the confusion and delay which might 
arise from changi ng the position of the troops, to 
meet the movements of the enemy, particularly in 
a night attack, would be extremely hazardous. 

289. A vigorous defence will require, at least, 
two ranks to be drawn up on the banquette 
throughout the entire extent of the line, with sup¬ 
ports, and a reserve proportioned to the importance 
of the work. 

290. The strictest vigilance should be exerted to 
guard against a surprise ; for this purpose sentries 
should be posted on all of the most commanding 
points of the works; and on the exterior, at such 
points as the enemy might approach unseen, as roads, 
fords, defiles, bridges, &c.; besides these, small 
detachments of picked men should be stationed to 
watch these accessible points, and all other places 
where the enemy might secrete himself, or approach 
unexposed to the fire of the works. Patroles should 
be sent out to watch the enemy’s movements, and 
to have an eye on the manner in which the sentries 
perform their duties. The patroles are particularly 
charged with the duty of preventing the enemy from 
reconnoitring the approaches to the works; to do 
which effectually, without giving unnecessary 
alarms, they should be ordered to attack with the 
bayonet alone, unless surprised by an ambuscade. 

291. At night the number of sentries should be 
increased ; and redoubled vigilance be used, par¬ 
ticularly after midnight. If there are well grounded 
apprehensions of an attack , fire-balls may be thrown 
out, or fires be lighted in front of the works, to dis¬ 
cover the approach of the enemy. Occasional false 
alarms should be made to keep the garrison on the 
alert; but this artifice should not be too often prac- 


101 


tised, otherwise it might produce a contrary effect; 
besides all useless fatigue should be spared men 
who are sufficiently harassed by the ordinary duties 
of their situation. 

292. In conducting the defence, each corps should 
have its particular post assigned to it; and receive 
special instructions relative to the part it will have 
to play. Too much attention cannot be bestowed 
on the part of the commanding officer in seeing that 
his subordinates are thoroughly conversant with the 
character of the defences, and of all the resources 
that can be drawn from their position ; and that this 
knowledge be imparted by them to the non-com¬ 
missioned officers, and even to the most intelligent 
among the privates. The fate of a work may 
depend upon the good or bad conduct of one indi¬ 
vidual. The reserve is posted in the most conve¬ 
nient position to afford prompt assistance to any 
point in danger of being forced. The troops drawn 
up on the banquette should be carefully instructed 
in their duties; and they should be taught not to 
look for aid, or relief, from the reserve, until they 
have repulsed the enemy. 

293. If the enemy opens his attack by a warm 
cannonade, the troops should not be exposed to it, 
if they can be sheltered near the posts they are to 
occupy when his columns of attack approach, at 
which time his cannonade must cease, in order not 
to injure his own troops. The men should be 
instructed to reserve their fire until the enemy has 
arrived at certain points marked out in front ot the 
works, which should not be farther than two hun¬ 
dred yards from the parapet. 

294. Sorties, if well '* 1 i 


the fate of the affair. 





9 * 


102 


the column is thrown into confusion, or shows any 
signs of irresolution in its movements; or when its 
flank, or rear, is carelessly exposed. They are 
sometimes made to alarm the enemy for his own 
safety; or to make a diversion in favor of expected 
succors in blockaded posts. 

295. Cavalry is the best arm for a sortie, on 
account of the rapidity of its movements, and the 
violence of its shock. When infantry is employed 
for this purpose, it should use the bayonet alone. 

296. Should the enemy succeed in forcing his 
way into the work, the reserve should attack with 
the bayonet, before he has time to form ; but it must 
be confessed that success oftener crowns an offen¬ 
sive movement, on the part of the assailed, in 
endeavoring to regain possession of their works, 
than any effort to drive back the enemy at the mo¬ 
ment, when flushed with success, he has the hope 
of a certain victory. The only well-grounded pros¬ 
pect that the assailed have of repelling the assault, 
when the enemy has gained the top of the scarp, is 
to meet him in an offensive attitude at the point of 
the bayonet on top of the parapet. 

297. The particular arrangements of the defence 
consist in defending all obstacles, such as abattis, 
palisadings, &c., by a warm well-aimed fire ; as the 
particular object of these obstacles is to keep the 
enemy exposed for a longer time to the fire. 

298. Large stones, heavy round logs, and loaded 
hollow projectiles, should be in readiness to be rolled 
over on the enemy whilst he is in the ditch endea¬ 
voring to mount the scarp. Large branches of trees 
prepared as for an abattis, with chevaux-de-frise, the 
other obstacles, should be at hand to obstruct the 
breach. 


103 


299. Finally, in an isolated post, if the enemy, 
after having been repulsed, makes a show of block¬ 
ading it, or of renewing his attack, and there is no 
prospect of succor arriving, the garrison should 
attempt an escape by night. 




END OF THE FIELD FORTIFICATION* 


’ m T 


CHAPTER XII. 

MILITARY COMMUNICATIONS. 

300. Despatch is of the first importance in all 
military operations; and nothing contributes more 
to it than the means of opening practicable and 
easy communications in every direction. 

301. Among the various obstacles by which the 
free movements of an army may be embarrassed, 
water courses, marshes and swamps, hold the first 
rank, owing to the difficulty of finding suitable 
means at hand to pass them, or of transporting 
those means in the train of an army. 

302. For the passage of water courses, bridges 
must be constructed; the character of the con¬ 
struction depending on the nature of the river, the 
particular locality selected for the bridge, and the 
means at hand. 

303. Before adopting definitively the particular 
locality, the officer charged with the construction 
should endeavor to gain the most accurate inform¬ 
ation, on every point, which might in any manner 
bear upon this selection ; for which purpose he will 
cause a reconnaissance to be made, to determine 
the breadth and depth of the river, and the character 
of its bed ;—the velocity of the current, the seasons 
of freshets, with their usual extent and effects;— 
the character of the banks, their absolute and rela¬ 
tive heights, their slope, the approaches to them, 
the distance between them and the water way, and 
finally, if they are wooded or otherwise ;—the po¬ 
sition and size of islands, whether wooded or not; 
—the extent of fords, their depth of water, and the 


105 


nature of their bottom;—the form and dimensions 
of elbows and indentations ;—the artificial obstruc¬ 
tions, or dams, &c., the possibility of their being 
destroyed by the enemy, and the practicability of 
applying them to the purposes of artificial inunda¬ 
tions ;—the position, extent, and character of the 
affluents ;—a description of the permanent bridges, 
and ferries ;—whether the river empties itself into 
the sea, or into another river, the extent and effects 
of the tide water ;—the nature of the permanent 
and temporary defences along the river ;—the kind 
of boats used in navigating the river, and the time 
it would require to collect them at a given point;— 
the proximity of forests to its banks, and the facili¬ 
ties afforded by them for constructing rafts. 

304. As a general rule, the elbows, which pre¬ 
sent their concavity to the side from which the pas¬ 
sage is to be made, are the best positions for the 
bridge, as being most favorable to the defence ; but 
it must be observed that, when the bridge is to re¬ 
main any length of time, the effects of the current 
on the banks, at the elbow, should be carefully as¬ 
certained ; these effects usually consist in washing 
away the banks on the concave side, and transport¬ 
ing the fragments to the opposite shore, thus deep¬ 
ening the bed on that side, and filling it up on the 
other. 

305. Military Bridges. Any structure raised 
especially for the purpose of affording a passage to 
troops across a river, may be termed a military 
bridge; but the expression is generally restricted 
to those temporary expedients for the same end, of 
whatever character they may be, to which an army 
is obliged to resort during the active operations of 
a campaign. 

3U6. The means most frequently resorted to, for 


106 


ine passage of troops over a river, is a floating 
bridge. This construction consists of boats, rafts, 
casks, or other buoyant bodies, anchored at suitable 
distances apart, to serve as points of support to the 
bridging proper, which is formed of beams, resting 
on the supports, to which they are firmly connected, 
as well as with each other, and of a flooring of 
plank laid across the beams, and fastened to them. 

307. Any buoyant body may be used for the 
supports, but experience is in favor of large flat- 
bottomed boats, termed bateaux , as presenting more 
advantages than any other. In Europe, bateaux, 
termed 'pontoons , which consisted of a framework 
of light wood, covered on the bottom and sides with 
tin, or copper, were for a long period mostly in use 
as a part of the bridge train of an army; but they 
have gradually gone out of use, and the French 
particularly, whose corps for the construction of 
military bridges, termed the pontooneers, is justly 
held in the highest estimation, as the most scientific 
and experienced in Europe, have adopted the bateau 
of uniform dimensions, with corresponding equip¬ 
ments, for its army boat train. 

308. As it is not the object of this chapter to 
enter fully into the subject of military bridges, which 
more properly belongs to a separate treatise, it will 
be confined to describing only such as troops, the 
least skilled, may construct under the guidance of 
an intelligent officer. 

309. The general properties of all bridges should 
be strength, stability, and, if they are to be trans¬ 
ported on land, lightness. 

310. The strength will depend on the nature of 
the points of support; and on the cross section ol 
the beams, and their bearing , or the distance, b% 
tween their points of support. 


107 


The strength should be such as to resist the 
action of the heaviest loads on the bridge, and also 
that arising from the current, the waves, and the 
wind. 

311. The essential requisite for the strength of 
a floating bridge is, that it shall not be loaded with 
a weight sufficient to injure the timbers or to sub¬ 
merge it. To ascertain the greatest weight that a 
bridge may be required to bear, the following data 
may be taken. The average weight of a foot 
soldier, with his arms, may be assumed at two 
hundred pounds; and the lineal space occupied by 
each man, when marching by a flank, eighteen 
inches ; a cavalry soldier, with his horse and equip¬ 
ments, may be taken at fourteen hundred pounds, 
and he occupies about nine lineal feet in file; a 
twelve-pounder gun with its carrage, limber, six 
horses, and three drivers, weighs about eleven thou¬ 
sand six hundred pounds, and occupies about forty 
lineal feet in march. The weights here given are 
rather over estimated, so that any error may be on 
the safe side. 

312. The term bay is applied to the interval 
between any two points of supports of a bridge, 
estimating this distance between the middle points 
of the supports; for example, in bateau supports, it 
would be from the centre line of one bateau to the 
centre line of the other. If we suppose this bay to 
be forty lineal feet, a very simple calculation will 
show, that when infantry is marching by a flank, in 
the ordinary formation of three ranks, there will be 
about eighty men on the bay, or sixteen thousand 
pounds in weight; and comparing this with the 
weight of either artillery or cavalry, it will be found 
to exceed them both. This may therefore be as* 


108 


Burned as the greatest weight that the bridge wil! 
have to bear on each bay. 

313. By a principle of hydrostatics, the weight 
of the volume of water displaced by a floating body 
is equal to the weight of the body itself; if, there¬ 
fore, the cubic contents of the part of a bateau, 
which is above the water line after the bridge is 
finished, be estimated, and this volume be multiplied 
by sixty-two-and-a-half pounds, the weight of a cubic 
foot of water, the result will show the weight, which, 
in addition to that of the bridge, would submerge it; 
and as the weight, placed on each bay, is borne by the 
half of each bateau of the bay, it follows, that if a 
weight, thus obtained, were laid on each bay, it 
would submerge the entire bridge. Now, in prac¬ 
tice, it is found that a bridge cannot bear with safety 
a weight greater than three-fourths of four-fifths of 
that which would submerge it. This consequently 
will furnish a ready means of comparing the weight 
that would submerge a bridge with what it can 
safely bear. 

314. To secure the stability of the bridge, every 
precaution should be taken to prevent an oscillating 
or undulating motion in any direction. These pre¬ 
cautions will, moreover, add to the strength of the 
bridge, as the connection of the parts will be firmer, 
and the weight consequently more uniformly dis¬ 
tributed over the supports. 

315. Oscillations in a lateral direction are pre¬ 
vented by anchors placed above and below the 
bridge, to which the supports are moored. The ob¬ 
ject of the up-stream anchors is, principally, to re¬ 
sist the action of the current.,, and of those down¬ 
stream to resist that of the winds and waves. The 
number, in each case, will therefore depend on the 


109 


force of the current and on the width of the river 
and its exposure to high winds. 

316. The inclinations of the cables, by which the 
supports are attached to the anchors, should be the 
same for all; so that they may offer a uniform re¬ 
sistance to a pitching motion. This inclination is, 
ordinarily, taken one-tenth ; that is, the distance of 
the anchor, from the support, is ten times the depth 
of the water. When the width of the river, and 
the nature of its banks, render it practicable, a 
cable is stretched across it, by means of a windlass, 
and the supports are either attached to this cable, 
by separate fastenings, or else the cables which at¬ 
tach them to the anchors are passed over and fast¬ 
ened to it. 

317. Undulations in a longitudinal direction are 
prevented by connecting the beams firmly to each 
other, and to the points of support. This connec¬ 
tion will also increase the strength, by diffusing the 
weight thrown on one support over several. The 
manner of regulating the passage of troops will, in 
a great degree, contribute in preventing this mo¬ 
tion. Infantry should always pass in open order, 
and with the route step ; cavalry should dismount 
and lead their horses ; and artillery, in some cases, 
should be drawn over by men. 

318. Lightness is an essential quality in the 
bridge equipage which is to follow an army, but 
it should always be subordinate to strength and sta¬ 
bility. 

319. Bateau Bridge. As the bridge equipage of 
the French is considered the best arranged, a de¬ 
scription of the bridge itself will be here given, 
to convey a more complete idea of this kind ol 
structure. 

320. The bateau is thirty-one feet long, two feel 

10 



110 


six inches deep, five feet four incnes wide at top, 
and four feet wide at bottom. It is built something 
like a skiff', the head and stern being a few inches 
higher than the body ; the width at the head being 
two feet, and at the stern four feet. The ribs are 
of oak; the bottom and sides of pine plank one 
inch thick. 

321. The beams, termed balks, which are laid 
abross the bateaux, are of four-and-a-half inch 
scantling, and twenty-five-and-a-half feet long. 

322. The flooring of the bridge is formed of 
boards, termed chesses, cut in lengths of fourteen 
feet, the width being twelve inches, and thickness 
one-and-a-half inches. 

323. The bateaux, when the bridge is formed, 
are thirteen feet ten inches apart, making the dis¬ 
tance between their centre lines, nineteen feet two 
inches. 

324. Each bay has five balks, the centre lines of 
the balks being two feet ten inches apart; and the 
ends of the balks project six inches beyond the 
outside gunwales of the two bateaux on which 
they rest. 

325. To confine the chesses to the balks, pieces 
of scantling, termed side-rails, are placed on them, 
over the outside balks, to which they are fastened 
by a cord, by what is termed a rack-lashing. 

326. The distance between the side rails is about 
eleven feet, and is the width of the free road-way. 
The chesses project equally beyond the outside 
balks. 

327. Before the construction of the bridge is 
commenced, a road-way of easy access, the slope of 
which may be only one-sixth, should be cut through 
the banks if necessary. An abutment is then form¬ 
ed by laying a heavy beam in a horizontal position 


Ill 


perpendicular u> the direction of the budge. The 
length of this beam should be the same as the 
chesses ; it is imbedded in the earth, on the same 
level as the top of the bridge, and is confined in its 
place by a stout picket driven at each end of it, and 
by two others driven in front of it. A chess is 
laid flat behind the beam, and with it constitutes the 
abutment. 

328. To give the proper alignment to the bridge, 
a staff is placed at a short distance from the abut¬ 
ment in the direction of the centre of the bridge, 
With another some yards in the rear of it and on 
the same line. 

329. ' The bateaux are placed in the water below 
the point which the bridge is to occupy, and they 
are brought successively into their proper position, 
as the bridge is carried forward from the share. The 
first bateau is placed, when the depth of water will 
admit of it, so far from the abutment that the balks 
resting with one of their extremities on it, the others 
will project six inches beyond the outside gunwale 
ol the batteau. The positions of the outside balks 
are shown by 'pintles placed in the gunwales. The 
chesses are laid on within one foot of the first ba¬ 
teau ; the position of the second bateau is then de¬ 
termined, and the balks of the next bay are laid; 
the precaution being taken to lay all the balks of the 
second bay either on the up-stream, or the down¬ 
stream side of those of the first bay. The chesses 
of the second bay are then laid, within one foot of 
the second bateau, and the construction is thus 
regularly carried on. 

330. As the balks are laid they are fastened to 
each other, and also to the bateaux, by a rack-lash¬ 
ing ; iron crotchets being placed on the inside of the 
bateau for this purpose. 


112 


331. The bateaux are fastened to each other by 
two spring lines , stretched diagonally from the head 
of one bateau to the stern of the other, through iron 
rings placed in suitable positions on the outside of 
the bateaux. The four bateaux nearest the shore 
are tied to strong stakes on shore by two ropes for 
each bateau, one up-stream, the other down. An 
anchor is allowed up-stream to two bateaux, and 
one down-stream to four. 

332. When a cable, or sheer line , can be stretch¬ 
ed across the river, before commencing the bridge, 
the preceding operations will be greatly expedited ; 
each bateau being attached at once to the cable, by 
ropes termed head-lashings. 

333. The side rails are laid so soon as the third 
bay is commenced ; they are fastened to the outside 
balks by a rack-lashing; the chesses being so ar¬ 
ranged as to admit its being passed between them. 
Each rail should be tied at its middle point, and 
near each of its ends. 

334. When the flooring is completed, it is cover¬ 
ed either with a thin layer of straw, or sand, to 
protect it in some degree from wear and tear. 

335. The bridge here described underwent a 
series of rigid experiments to test its properties; 
the results of which were of the most satisfactory 
character, as to its strength, stability and lightness. 

336. When the bridge was completed the draught 
of the bateaux was nine-and-a-half inches ; when 
traversed by a column of infantry three abreast, 
marching with the cadenced step, and in close order, 
the draught of the bateau was one foot seven inches, 
and was the same when crossed by a twenty-four- 
pounder, drawn by eight horses, with their drivers. 

337. Its travelling equipage can follow in the 














' 
























1 

































EXPLANATIONS OF PLATE X. 

Fig G5. Shows a section and an elevation of a defensive wail, 
with 'wo tiers of fire ; cc 1 is a platform, on trestles 
a a' for firing over the top, with a wooden ramp, b b' 
to ascend to it; d d' are the lower loop-holes, with a 
ditch behind the wall to admit firing through them. 

Fig. 66. Shows a plan of a defensive wall, a ; flanked by a 
Tambour, b. 

Fig. 67. Shows a section of the wall of a house through a win 
dow, and a Machicoulis ; a are horizontal pieces on a 
level with the floor, fastened to it by a horizontal 
cross-piece, b, or by lashing them to the joists, d ; c 
are uprights fastened to the cross-pieces on which 
thick planks are nailed to form a parapet. 

Fig. 68. Shows a plan, a longitudinal, and a cross section of a 
Bateau Bridge ; a are the bateaux; b the Balks, c 
the Chesses; d the Side Rails; e the Abutment; f 
the Cross Lashing; s stakes to which the shore ba¬ 
teaux are moored. 









































































































































































































































113 


train of an army with the same ease as a twelve- 
pounder. 

338. A bridge across a navigable stream should 
admit a free passage to the river craft; for this 
purpose a part of the bridge, resting on one or two 
bateaux, should be so arranged that it can be slipped 
out of its place, forming a draw for the passage. 

339. To break up the bridge, the operations are 
the reverse of those for laying it. The operation 
is commenced at the shore to be abandoned ; the 
side rails, chesses, balks, &c., are taken up in their 
proper order, and conveyed to the opposite shore, 
either by hand, or in the bateaux. 

340. On narrow rivers, with a gentle current, 
this operation can be greatly expedited by detaching 
the entire bridge from its moorings, and allowing it 
to swing round against the shore. To perform 
this manoeuvre with safety, two stout ropes, or guys, 
are attached, one to the stern, the other to the head 
of the second bateau, from the shore to be abandon¬ 
ed ; ten or twelve men are placed at each guy, to 
ease off, or belay , according to circumstances. An¬ 
other stout rope, attached to the fourth or fifth 
bateau, from the opposite shore, is drawn tight 
and fastened to a strong stake up-stream, at fifty or 
sixty yards from the bridge. When these prepara¬ 
tions are made, the head lashings are cast loose ; 
the two extreme bateaux are detached from their 
abutments; and the anchor cables are gradually 
eased off, to allow the bridge to swing round with a 
gentle uniform motion. 

341. This manoeuvre requires great care, and 
should not be resorted to, except in cases of neces¬ 
sity, unless the current is gentle, and there are not 
more than twenty-rive or thirty bateaux. The same 


10 * 


114 


means may be taken, under similar circumstances, 
to throw a briJge across a river. 

342. Boat Bridges. Flat-bottomed boats are more 
suitable than keel-boats for a bridge, owing to their 
greater volume, and their stability in the water; 
but when they cannot be obtained, keel-boats may 
be taken. If the gunwales are not suitable to serve 
as points of support to the balks, a framework 
should be placed in the centre of the boat for this 
purpose. The framework may consist of a sill- 
piece of six or eight-inch scantling, fitted to the 
bottom of the boat, and a cap-sill of the same di¬ 
mensions, which is supported at a suitable height 
by uprights of four-inch scantling mortised into the 
cap and sill pieces. This frame is kept in place by 
struts, of the same sized scantling as the uprights, 
which are placed against the uprights and ribs of 
the boat. 

343. The balks are laid on the caps, jutting 
about two feet beyond them, and are firmly 
secured to them and to each other by a rack¬ 
lashing. 

344. As the boats are generally of unequal size, 
two small boats may be, in some cases, lashed to¬ 
gether to form one support; and to bring them all 
to the same level, they may be ballasted with stone. 
The strongest boats should be placed at the ex¬ 
tremities of the bridge, as these parts are more 
liable to injury, from the motion of the bridge, than 
the middle. 

345. When anchors cannot be procured, mill¬ 
stones, strong baskets, or bags, filled with large 
round pebbles, or broken stone, may supply their 
places ; and, in shallow rivers, each boat may be 
fastened to stout stakes driven into the bed of the 
river. 


115 


346. Raft Bridge. Rafts formed of solid timber, 
or of casks, barrels, the skins of animals prepared 
and inflated, &c., are frequently used in military 
operations, either to construct bridges, or to serve 
the place of boats in the transportation of troops 
across streams. 

347. Timber rafts are particularly serviceable in 
wooded and mountainous countries, where, owing 
to the nature of the streams, boats cannot always 
be procured. A bridge may be constructed on 
rafts over rivers of any size, and may be made to 
bear any loads ; but, owing to the form and dimen¬ 
sions of the rafts, rapid currents present great dif¬ 
ficulties to their manceuvre whilst the bridge is under 
construction. 

348. The timber for a raft may be either square 
or round, seasoned or green ; in all cases, however, 
the lightest and best-seasoned wood should be pre¬ 
ferred as being most buoyant. 

349. To ascertain the weight which will sub¬ 
merge a piece of timber of given dimensions, the 
following method may be used: Take a cubical 
block, of any size, and ascertain its weight; fill a 
vessel with water, and immersing the block in it, 
find the weight of the water which it displaces ; 
the difference between the weight of the block and 
that of the water displaced, will give the weight 
which, placed on the block, would be sufficient to 
submerge it. If this difference be multiplied by the 
weight of a cubic foot of water, and the product 
be divided by the weight of the water displaced, 
the quotient will give the weight necessary to sub¬ 
merge a block of a cubic foot; therefore, multiply¬ 
ing this result by the number of cubic feet in the 
given piece, the product will be the total weight 
sought. 


116 


350. The cubic contents of the piece itself, if n 
be the trunk of a tree, may be found by adding into 
one sum the areas of the two ends, and four times 
the area of the section, at the middle of the trunk, 
and multiplying this sum by one-sixth the entire 
length. 

351. The weight of green wood is greatest when 
it is cut whilst the sap is running; and seasoned 
wood, when placed in water, is found to augment 
about one-sixth in weight, in a few days, unless the 
precaution is taken to tar the ends of the trunks ; 
and this increase of weight is found to be greater 
in wood that has been long cut than in new tim¬ 
ber. 

352. The volume of the raft should be in pro¬ 
portion to the weight of load that the bridge must 
bear; and the length and breadth, for the same 
volume, will be determined from the consideration, 
that the stability varies directly as the length, and 
inversely as the breadth ; therefore, the longest and 
largest trunks should be selected, since fewer of 
them will be required for the same load, and the 
length will thus be increased at the expense of the 
breadth. The length of the trunks should not be 
less than forty or forty-five feet, particularly if the 
current is rapid, otherwise there will be a very 
sensible oscillating motion of the bridge. 

353. Before constructing the raft (Fig. 69) the 
trunks are placed in the water, as they will there 
assume their natural position of stability, and they 
can be more easily moved about in it. The large 
ends of the trunks are cut away on their under 
side, like the shape of a child’s whistle. The trunks 
are then laid side by side with their butt ends to¬ 
gether, leaving about four inches between them, 
and so that they will project a little beyond each 


117 


other from the middle to the outside trunks, making 
an angle, of the perpendicular of which is one- 
fourth the base. The trunks are then united by 
four cross-pieces, one placed near each end, and 
two near the middle, about ten feet apart; the 
cross-pieces being fastened to the trunks, either by 
strong wooden pins driven into auger holes made 
through the pieces, or else by a strong rope-lash¬ 
ing. Three sleepers are laid across the centre 
cross-pieces, one over the middle of the raft, and 
the other two near the outside trunks; the object 
of these sleepers is to give the flooring sufficient 
elevation above the surface of the water to prevent 
the waves from breaking over it. 

354. The rafts are anchored by two anchors for 
each, one up-stream, the other down, the cables of 
which should be drawn tight to prevent any pitching 
motion. The rafts should be placed as far asunder 
as practicable, to allow a free passage to the water; 
this distance will depend chiefly on the size of the 
timber that can be procured for balks ; each balk 
should jut at least one foot beyond the middle 
sleepers of the two rafts on which it rests. The 
balks are secured to the sleepers and to each other 
by rack-lashings. The rafts should moreover be 
connected by a beam at the head and stern. 

355. The tendency of the current on the up¬ 
stream cables is to submerge the head of the raft; 
this tendency will be in part counteracted by plac¬ 
ing the butt ends up-stream, and by the manner of 
arranging these ends ; as a farther precaution, the 
flooring should be placed lower down-stream than 
the centre of gravity of the rafts, so that its weight 
may tend to raise the head of the rafts. 

356. On navigable rivers, a draw must be made 
similar to the one used for a boat bridge; but as 


118 


a raft-draw would not be easily manoeuvred, particu- 
larly in a strong current, it would be well to use a 
draw of boats. 

357. Rafts of empty casks, or inflated skins, 
may be made to bear any load, by lashing a suf¬ 
ficient number together. They cannot be relied on 
for a safe passage except on narrow and gentle 
streams. 

358. Flying Bridges. Any floating body which 
is propelled from one shore to the other by the force 
of the current alone, acting obliquely to its side, is 
termed a flying-bridge. But in order that the fly¬ 
ing-bridge shall cross and recross always at the 
same points of the shores, it must be held by a 
cable, attached to an anchor, either in the middle, 
or at some more suitable point of the stream. 

359. A flying-bridge, when arranged in the best 
manner, should bear the heaviest loads that the ser¬ 
vice may require ; it should be perfectly stable, and 
cross the stream in the shortest time possible. 

360. The most usual manner of forming a flying- 
bridge is to connect two boats, by a platform, con¬ 
sisting of joists laid across the boats, and a flooring 
of plank on the joists. The cable is attached to 
this platform, and passing over a cross-piece, sup¬ 
ported above the platform by two uprights, so as to 
sweep clear of the deck in the movement of the 
bridge, is secured at the other end by an anchor, or 
any other fixed point of support. 

361. The best form of boat is one with a long, 
narrow, flat bottom and sharp head ; the length from 
sixty to ninety feet; width, ten to fifteen feet, and 
depth, six to seven feet. These boats have great 
capacity, and present a large side surface to the 
action of the current. 

362. The distance between the centres of the 


119 


boats cannot be much greater than twenty-five te. 
thirty feet, owing to the usual dimensions of the 
beams used for joists, which will not generally ad¬ 
mit of a greater bearing. The length and breadth 
of the platform are about the same, and may be 
about fifty feet. 

363. The bridge may have two platforms, like the 
double decks of steamboats, and when arranged in 
this way, by proper management, it may be made 
to bear from one thousand to fourteen hundred in¬ 
fantry. 

364. The time of crossing will depend on the 
length of the cable, the position of the anchor, and 
the direction given to the head of the boat, by means 
of a rudder, whilst in motion. 

365. The cable should be at least equal to the 
width of the river, and experience has shown that 
the most suitable length for a quick passage is once- 
and-a-half the width. If the velocity of the current 
is the same on both shores, the anchor should oc¬ 
cupy the middle point of the stream; but if it is 
greater near one than the other, then it is best to 
place the anchor nearest to the shore where the ve¬ 
locity is the least, because in approaching that shore 
the position of the boat will be in favor of the les¬ 
sened action of the current. 

366. Ordinarily one anchor is deemed sufficient; 
but as the action of the boat will tend to shift the 
position of its shank, and consequently weaken the 
hold of its flukes, it would be better to place three 
together, the shank of the middle one being in the 
direction of the current, and those of the other two 
being respectively in the directions of the extreme 
positions of the cable. 

367. The height of the cross-piece, which sup¬ 
ports the cable, will depend on the velocity of the 


120 


stream, and the length of the cable; its object being 
to keep the cable clear of the platform. A height 
varying between twelve and thirty feet is generally 
sufficient. The best position of the cross-piece and 
its supports, is about one-third the length of the boat 
from the bow. One cross-piece is enough to sup¬ 
port the cable*; but as the motion of the boat would 
occasion rapid wear and tear, both of the cable and 
the cross-piece, a better arrangement consists in 
placing two cross-pieces, with a sliding pulley, or 
block , between them, the cable passing through an 
eye in the pulley. 

368. A windlass is placed on the platform, to¬ 
wards the stern, to which the cable is fastened ; it 
serves to let the cable out in case of danger, from 
the action of the current or wind, and to take up the 
slack when necessary. 

369. In shallow gentle streams, or in wide rivers, 
buoys, or narrow small decked-skiffs, are used to 
buoy up the cable, and prevent it from impeding the 
velocity of the bridge, by dragging on the bottom. 
They are placed about one hundred and twenty feet 
apart, their number depending on the circumstances 
of the case. The cable should be borne on small 
supports slightly elevated above their decks. 

370. Flying-bridges of boats, or rafts, abandoned 
solely to the action of the current, may be found 
very serviceable in effecting a passage by surprise ; 
the bridge is cast loose from the shore and directed 
on the opposite one, by means of an oar astern, to 
keep it in the proper position to receive the most 
favorable action of the current. The platform in 
this case may be surrounded by an enclosure of 
timber, or bags of wool or cotton, so as to be proof 
against the enemy’s musketry and case-shot in case 
of an alarm. 


121 


371. Trestle Bridge. The form of a trestle is the 
same as what is termed a carpenter'’s-horse, that is, 
a horizontal beam supported by four legs. 

372. The horizontal beam, termed the cap or 
ridge-beam, is usually of eight-inch scantling, and 
from twelve to sixteen feet long. The legs are of 
four-and-a-half-inch scantling; they have a spread 
towards the bottom, the distance between them 
across being equal to half the height, and length¬ 
wise of the cap, their inclination is one-twelfth of 
the height; they are fastened to the cap, about 
eighteen inches Trom the ends, by nails, the side of 
the cap and the top of the leg being properly pre¬ 
pared for a strong, accurate fit. The legs are con¬ 
nected either in pairs, or else all four by horizontal 
pieces of three-inch scantling; sometimes'diagonal 
pieces, going from the top of one leg to the bottom 
of the opposite one, are used. 

373. Bridges on trestles are principally useful in 
crossing small streams not more than six feet deep. 
They also serve to connect a boat bridge with the 
shore, in shallow water; and are used as the sup¬ 
ports for the bridges of communication across the 
wet and dry ditches of field works. They present 
the advantage of being formed of materials which 
can always be procured at hand, either by cutting 
down forest trees, or by demolishing the floors and 
partitions of houses. Moreover, when constructed 
of light wood, they may be taken to pieces, and be 
easily tram;ported on horses, or mules, in a wooded 
or broken country. 

374. The trestles should not be placed farther 
apart than sixteen feet between the ridge beams, for 
balks of the ordinary dimensions ; the balks should 
jut at least one foot beyond the ridge beams. Th« 


11 


122 


flooring, fastenings, &c., are the same as in a boat 
bridge. 

375. When the bed of the river is of soft mud, 
or is hard and uneven, it is difficult to place the 
ndfre beams horizontal; in the former case to make 
the legs sink equally, they may be let into sills, 
which should jut a few feet beyond them. 

376. The action of the current is counteracted, 
either by anchors, or else by attaching each trestle 
to two cables, stretched across the stream above 
and below the bridge ; stout stakes, or piles, might 
also be used for the same purpose. Another plan 
consists in making an open wattling , or a net work, 
of tough twigs, or cords, around the legs, near the 
bottom, and filling it in with broken stone. 

377. The best manner of placing the trestles in 
deep water is by means of a raft, or a boat, so pre¬ 
pared that the trestle can be readily lowered into 
the water over the side. 

378. Temporary bridges are readily constructed 
in wooded countries. The officer charged with 
establishing communications of this character, will 
always do well to imitate the ordinary constructions 
of the country, particularly if he has to employ the 
country people to form them. In swamps and 
marshy grounds, a road-way of timber or stout 
brushwood, or even of trusses of hay or straw, will 
frequently have to be resorted to. After opening a 
way of sufficient width, and cutting down the 
stumps, so as not to impede the passage of vehicles 
on wheels, the trunks of the largest trees are cut 
into lengths of about fifteen feet, and are laid across 
the line, at distances of ten or twenty feet apart; 
notches are cut into the cross-pieces, about eighteen 
inches from each end, and sufficiently large to re¬ 
ceive trunks of trees from nine to twelve inches in 


123 


diameter; these trunks should be cut into pieces 
of as great length as the tree will afford. Across 
these longitudinal pieces the bodies of small sap¬ 
lings, from three to four inches in diameter, and 
fourteen feet long, are laid, and small brushwood, 
earth, or straw, may be laid over them, to make the 
road-way more regular. In some cases the road¬ 
way may be formed by laying the saplings without 
any other substructure. 

379. Fords. Infantry can ford a stream when the 
depth of water is not greater than three or four 
feet; cavalry when the depth is not more than four 
feet; and artillery, a depth of two-and-a-half feet. 
In cases of great emergency, particularly in gentle 
currents, infantry and cavalry may pass fords of 
greater depths than those just laid down ; but safety, 
and a regard to keeping the ammunition in a good 
state, prescribe the depths here given. 

380. The bottom of a ford should be of solid gra¬ 
vel; if of mud, fine sand, or obstructed with large 
fragments of stones, the difficulty of passing car¬ 
riages and large bodies of troops will, generally, be 
found insurmountable. 

381. Fords are frequently met with near elbows, 
and usually in an oblique position to the thread of 
the stream. In making a reconnaissance for the 
purpose of seeking for a ford, a small boat should 
be allowed to float down with the current, and sound¬ 
ings be made. 

382. To prevent accidents whilst the troops are 
crossing, stakes should be placed in the direction of 
the ford, showing its width; ropes are fastened to 
these stakes, on a level with the water, to prevent 
loss of life. If the ford is crossed at night, lighted 
torches are tied to the stakes. 

383. If a large body of troops should cross, the 


124 


Infantry should pass first, the artillery next, and the 
cavalry last, so that the bottom may not be cut up 
by the feet of the horses. 

384. Ice. The heaviest guns may cross on ice 
which is six inches thick, and rests on the water 
under it; but, as a measure of prudence, plank 
should be laid under the wheels to distribute their 
pressure over a greater surface, and also to counter¬ 
act the effect of shocks. 

385. When the ice is but three inches thick, in¬ 
fantry and light guns can cross it with safety ; but 
the men should be sent across in small detachments, 
and plank, or straw, should be placed under the 
wheels of the guns and the feet of the horses. By 
sprinkling water over the straw, it will, by its 
freezing, form a more compact roadway. Heavy 
guns must be carried over on sleds, taking every 
precaution to distribute the weight of the load over 
a large surface. 

386. Ice which does not rest on water cannot be 
trusted to, unless it is at least six inches thick, and 
even then it should be crossed with great caution. 

387. An army should never trust either to fords, 
or to ice, for keeping open its communications ; for 
a freshet, or a thaw, would place it in the most cri¬ 
tical state. 

388. Preservation and Destruction of Bridges. 
Floating bridges are liable to injury from oscilla¬ 
tions, caused by high winds, and the crossing of 
troops ; from sudden freshets; and from the shock 
of floating bodies. 

389. Besides the usual means which are taken 
to insure strength, by preventing oscillations, the 
manner of conducting the passage of troops re¬ 
quires great attention. Infantry should pass in hall 
battalions, with an interval of forty or fifty paces 


125 


between each half battalion, and in order of route, 
by a flank. Cavalry should dismount, and lead 
their horses, leaving forty or fifty paces between 
each squadron. Carriages should not cross at the 
same time as troops, and in no case should they be 
suffered to pass each other; the intervals between 
them will depend on the weight of each. Finally, 
the pontooners should be at their posts, to keep the 
cables and spring-lines well stretched, and to tight¬ 
en the rack-lashings. 

390. A firm anchorage, and a solid construction, 
are the best securities against the action of high 
winds, and the sudden rise of the river. To pre¬ 
vent the effects of the latter, the pontooners ease 
off the cables as the river rises ; and when danger 
is apprehended for the safety of the bridge, it must 
be cast loose, and suffered to swing round to one of 
the banks, every possible precaution being taken to 
prevent its gaining a great velocity during the 
movement. 

391. Pumps and scoops should be provided to 
bail out in case of leaking or the breaking in of the 
waves. 

392. In shallow streams, a stockade may be 
formed, either obliquely across the river, or else 
with an angle up-stream, at four hundred or five 
hundred yards above the bridge; strong cables, or 
chains, are attached to the stockade, on a level with 
the water, to arrest heavy floating bodies, which 
might injure the bridge by striking against it. In 
deep water a boom must be placed to secure the 
bridge. The strength and character of the boom 
will depend upon the probable means the enemy 
may have for breaking through it. In some cases 
a heavy chain buoyed at intervals by logs, or a 
strong cable sustained in a similar way, and fasten- 


126 


ed by ropes to anchors, may be requisite. In others 
heavy logs firmly secured to each other at their 
ends by chains may offer sufficient security. The 
ends of the boom must be strongly attached to large 
piles driven into the banks. 

393. Posts of observation are placed to watch 
the stockade, or the boom. They are provided with 
boats, ropes with grapnels, and a few pieces of ar¬ 
tillery, for the purpose of arresting all floating 
bodies. 

394. If a flying-bridge is placed in connection 
with the boat-bridge, it should always be below it; 
so that no accident may occur from the flying-bridge 
parting from its cable. 

395. To destroy a bridge of the enemy, heavy 
floating bodies, f re-boats, and infernal machines , are 
resorted to. 

396. When the object is to destroy the bridge by 
a shock, a raft is formed of several large trunks of 
trees. A short and strong mast is strongly attached 
near the head of the raft, for the purpose of carry¬ 
ing away the flooring, if the raft should pass be¬ 
tween the intervals of the boats. Large boats, 
heavily laden with stones, may be used for the 
same ends; the object in both cases being to acquire 
sufficient momentum to destroy the bridge. 

397. Fire-boats loaded with combustible matter, 
are sent down with the current to burn the bridge. 
Hollow projectiles, heavily charged with powder, 
are placed in the fire-boats to deter, by successive 
explosions, the pontooners from approaching them. 
Infernal machines are arranged so as to explode by 
the shock of the boat against the bridge. 

In an attempt to destroy a bridge by these means, 
a number of them should be sent down at once, to 
increase the chances of success. They are con- 


127 


i 


ducted by boatmen as near to the bridge as they 
can approach with safety, and are then abandoned 
to the action of the current. 

398. When a bridge is no longer of service, it 
may be destroyed, to prevent its being of use to the 
enemy, either by sinking it, burning it, or blowing 
it up. Combustible matter and cannon will serve 
for the two first mentioned methods, and a barrel 
or two of powder, placed below the flooring, and 
fired by means of a powder-hose, or a slow-match, 
will answer for the third. 

399. A stone-bridge can be destroyed by making 
a trench, eighteen inches deep, across the road-way, 
over the crown of an arch ; placing three hundred, 
or four hundred pounds of powder in it, and cover¬ 
ing it over with plank, and a heavy weight of earth, 
and exploding it by means just mentioned. Or, if 
pressed for time, several barrels of powder exploded 
at the same time in the open air, over the crown, 
will effect the same purpose. 

400. Passage of Rivers. There is no military 
operation of a more delicate character, and of more 
doubtful success, than the passage of a river in the 
face of the enemy, whether acting offensively, or in 
retreat. 

401. A passage by main force must always be 
accompanied by the most bloody results, if the ene¬ 
my displays even ordinary courage and good con¬ 
duct ; and it cannot be attempted, with the slightest 
prospect of success, unless the troops are covered 
by a very superior artillery, so posted as to cross 
its fire in advance of the point where the passage 
is to be effected, to prevent the enemy from charg¬ 
ing the troops in the act of disembarking, before 
they can form in order of battle. The main diffi¬ 
culty in this operation consists in getting the troops, 


128 


first landed, to stand firm until, by successive rein¬ 
forcements, they find themselves in sufficient 
strength to advance on the enemy. And the best 
plan to gain this indispensable time, if the ground 
be favorable, is to throw over some squadrons of 
cavalry among the first, whi-ch, by successive 
charges, may keep the enemy at a distance. 

402. In attempting a passage, by main force, a 
point must be selected on the opposite shore where 
the banks are not steep, wooded, or broken, and 
where the water is sufficiently deep to float the 
boats to a firm landing, in order that the troops 
may be able to form readily in order of battle, and 
to push forward without danger from a surprise. 

403. When the opposite shore is occupied by 
the enemy in force, and is vigilantly guarded, there 
remains no way to effect a passage but by stratagem. 
To effect this, the bridge equipage is transported, 
secretly, to some point near that where the passage 
is to be made. If there are affluents near this 
point, or islands, they may be taken advantage of to 
launch the boats undiscovered, and even to construct 
the bridge in parts which are afterwards floated to 
their position and put together. Demonstrations 
are made on several points, by the army, to draw 
off* the enemy’s attention from the real point, and 
troops are thrown over, after night-fall, in row-boats, 
and on flying-bridges; and the bridge is immedi¬ 
ately commenced, and should be in readiness for the 
passage of the army by early dawn. 

404. To protect the operation from a surprise, 
the troops first thrown over should occupy all the 
most accessible approaches, within twelve hundred 
or fifteen hundred paces, in advance of the point of 
passage; and other troops should throw up a slight 
intrenchment, like the 'parallel used in a siege, 


129 


about two hundred paces in advance of the ground 
to be occupied by the tete-de-pont. The object of 
these works is to keep the enemy off, should he pre¬ 
sent himself in force ; and to gain time for all the 
army to pass over, and form, without confusion, 
in order of battle under cover of these first disposi¬ 
tions. 

405. A retreat across a river is necessarily made 
in the face of the enemy; and here, more than in 
any other position, an army is called on to show the 
coolest and most determined courage, for its safety 
depends on the strictest observance of good order. 
After the bridges are ready, and the tete-dq-pont is 
in a defensible state, the movement of retreat com¬ 
mences, under cover of batteries of heavy guns on 
the opposite shore, these batteries having been 
thrown up at the earliest opportunity, and placed to 
take the enemy in flank. 

406. The garrison of the tete-de-pont forms the 
rear guard, and retires last, leaving a few compa¬ 
nies of grenadiers in the stoccade works, at the 
head of each bridge, for the protection of the pon- 
tooners, whilst they are preparing the bridge to be 
swung round. 

In a retreat, a single bridge should never alone 
be relied on, as the slightest accident happening 
to it might compromise the safety of the whole 

army. 


CHAPTER XIII. 


MILITARY RECONNAISSANCES. 

407. By the term Military Reconnaissance , is 
understood a detailed examination of any extent of 
country, whether large or small, with a view of 
ascertaining its resources for the movements and 
subsistence of troops. This examination may be 
of a special nature , as, for example, a proposed line 
of march; the character of a defile, river, or an 
enemy’s position, &c.; or it may have a more 
general bearing, as the collecting of information for 
an entire campaign, or the exploring of a large 
district of country. 

408. The importance of accurate reconnais¬ 
sances, of whatever nature they may be, cannot be 
too strongly insisted upon; for all military opera¬ 
tions must be based upon them, and any oversight, 
or neglect, in this respect, may involve the safety 
of an army, and through it the destinies of a nation. 

409. When the reconnaissance is of a special 
character, the officer charged with it should confine 
his operations strictly within his instructions, and 
not waste time upon any object which might with 
propriety be brought into view in a more general 
reconnaissance; but when the object is to obtain 
information for the operations of a campaign, or for 
distant expeditions, nothing should be overlooked 
which may bear, even in a remote degree, on the 
movements and subsistence of an army. 

410. A reconnaissance consists of two parts* a 
map, and a descriptive memoir. 

411. The map should exhibit the topographical 


131 


features of the country; and the memoir should 
supply whatever features cannot be shown on a 
map, and also furnish information on the resources 
of the country for the subsistence and movements 
of troops. 

412. The style of the memoir should be concise 
and clear; and nothing should be contained in it 
which is not strictly relevant to the object in view. 
The information furnished by it should be, first, 
those topographical features which a map cannot 
so well exhibit, as the nature of the face of the 
country; the quality of the soil; the height and de¬ 
clivities of mountains ; on what side they are acces¬ 
sible, and for what kind of troops, and the means 
of transportion over them ; the character of forests, 
water courses and other obstacles. Second, the 
lines of communication, as roads, rail-roads, canals, 
navigable streams, and all the circumstances in 
connection with the subject of transportation ; the 
advantages and defects of military positions for the 
offensive or defensive. Third, everything which 
relates to the culture and produce of the country ; 
its fertility or barrenness; its resources in provi¬ 
sions and forage ; the size and population of the 
cities, towns, villages, &c. Fourth, the commercial 
and manufacturing resources of the country; the 
number of mechanics of the different trades that 
are most necessary for the supplies of troops. 

413. Such is an outline of the operations of re¬ 
connaissances in general; and from it may be 
gathered the acquirements which the officer, 
charged with making them, is supposed to possess. 
To a familiar acquaintance with the duties of the 
topographical engineer, he should unite a large 
fund of general information on statistics and the 


132 


natural sciences ; a fund which nothing but a life 
of daily study and observation can supply. 

414. The reconnaissances required by the daily 
operations of a campaign, are usually of a special 
character; such as examining a line of march or a 
military position. A special reconnaissance con¬ 
sists, for the most part, of a sketch in pencil, made 
with all the accuracy that the means at the disposal 
of the officer admit of; and a memoir. 

415. Before commencing the reconnaissance, 
all the previous information, which can be obtained 
from maps, and published descriptions of the coun¬ 
try, should be carefully collected, and afterwards 
compared with the officer’s operations; this will 
serve, not only to abridge the labor, but also to give 
greater or less confidence in the published informa¬ 
tion on parts which cannot be examined for want 
of time, or from other causes. 

416. In examining the face of the country, 
carriers, wood-cutters, hunters, trappers and Indians, 
are the best persons to apply to for information, and 
they should be chosen for guides. To obtain infor¬ 
mation on the resources of the country, magistrates, 
clergymen, inn-keepers, tax-gatherers and farmers, 
should be questioned ; but from whatever source 
the information may be derived, it should be re¬ 
ceived with due caution, and only be acted on when 
confirmed by strict cross-examination of all the par¬ 
ties from whom it comes. 

417. The nature of a special reconnaissance has 
already been shown in the two preceding chapters, 
and but little more need therefore be added under 
this head ; particularly, as special instructions, ar¬ 
ranged under a tabular form, should always be sup¬ 
plied to the officer, charged with the operation, both 
as a guide to himself, and to enable the officer to 


133 


whom the report is made to see at a glance the 
exact state of the case. 

418. The reconnaissance of the enemy’s posi¬ 
tion is one of the most important of a special na¬ 
ture. The officer charged with this service should 
be thoroughly skilled in the duties of out-posts; as 
his operations must, in most cases, be carried on 
under the protection of a detachment, subject to his 
orders. In performing this service, he should never 
lose sight of the sole end in- view, the obtaining of 
information on a particular point , and all his dispo¬ 
sitions should be made to attain this end. For this 
purpose he must vigilantly guard against a surprise, 
and avoid an action with the enemy, unless the 
safety of himself and his detachment shall render it 
necessary; for the procuring of the required intelli¬ 
gence, which is to regulate the movements of the 
entire army, is paramount to every other conside¬ 
ration. 

419. In reconnoitring the enemy’s position, the 
extent of the ground which he occupies, and its 
character, should be first ascertained; the charac¬ 
ter of the approaches to his position, and the dis¬ 
posable means that can be found at hand to take 
advantage of the approaches ;—the disposition of his 
troops, and the arrangement of his defences ;—the 
towns, villages, and other unoccupied sites along 
his line which might be occupied with advantage 
by either party;—the character of his line of re¬ 
treat, and the defensible positions in his rear;—the 
possibility of turning his position, and cutting his 
line of operations. In conducting this examination, 
the officer, of course, will be called upon to make 
other special reconnaissances of a more minute cha¬ 
racter ; on the nature of the roads, by-paths, bridges, 
defiles, rivers, fords, marshes, swamps, forests, &c.; 

12 


134 


in which will be minutely stated the facilities they 
may severally afford, and the obstacles they present, 
to the movements of troops of all arms. The form 
of these minute examinations must be furnished the 
officer; for no presence of mind, and tenacity of 
memory, are sufficient to call to mind all that is ne¬ 
cessary to be done in an operation which, from its 
very nature, must be of a hurried character. 

420. A reconnaissance of a position to be de¬ 
fended temporarily, or to be occupied as an in¬ 
trenched camp, is made with the same care as one 
for offensive operations. It should state, not only 
the advantages and defects of the position itself, 
but should point out the character of other positions 
in its rear, that might be occupied to check the 
enemy’s progress, should he force the first. 

421. The Military Sketch of a reconnaissance 
should be made with all the accuracy that the means 
at the officer’s disposal will admit of. Surveying 
instruments are not always to be found in an army, 
and their places must be supplied by the officer’s 
own ingenuity; distances are ascertained approxi¬ 
mately, either by pacing them off with a uniform 
step, and estimating them by the length of the pace, 
or by the time required. The position of objects 
may be laid down by the intersections of lines, or 
by estimating in a rough manner the angles be¬ 
tween different points. Slopes and declivities may 
be judged of by the greater or less time which it 
may take a man, or a horse whose action is well 
ascertained, to ascend or descend them. 

422. A pocket sextant , a small protractor , and an 
ivory scale , are invaluable instruments for this ser¬ 
vice. They not only furnish the means of greater 
accuracy, but they essentially abridge the labor and 
time required with less complete means. 


CHAPTER XIV. 


•CTLINES OF THE GENERAL PROPERTIES OF PER- 

MANENT WORKS AND THE METHOD OF ATTACKING 

THEM. 

423. The term Permanent Fortification be longs 
to that branch of the Art of Fortification where 
means of a durable character are used to strengthen 
a position. Permanent differs from Temporary 
Fortification, not only in the character of the means 
used, but also in offering a more formidable ob- 
stacle to the enemy from the greater strength of its 
profile. 

424. This difference occasions a great disparity, 
both in the measures and the time required for the 
attack of permanent and field works. In the latter, 
a hasty assault decides the fate of the affair; in the 
former, the enemy is obliged to provide vast re¬ 
sources both of men and materials, and to approach 
the work attacked slowly, and with the greatest 
caution, under the cover of intrenchments, by which 
his troops are sheltered from the fire of the work, 
and he is enabled leisurely to destroy its defences. 

425. Permanent works may be divided into two 
general classes, Fortresses and Forts. The term 
fortress is applied to fortified towns alone, and the 
term fort, to a work containing only a garrison. 

426. The character of the fortification is the same 
in both classes ; consisting, in its most simple form, 
of an elevated and wide mound of earth, termed the 
rampart, which encloses the space fortified, of an 
ordinary parapet surmounting the rampart, and of a 
wide and deep ditch w r hich surrounds the whole. 


136 


427. These parts of the profile serve the same 
purposes as the corresponding parts in the profile 
of a field work; the most striking difference be¬ 
tween the two consists in the rampart, which, from 
its height, gives a very commanding position to the 
parapet, and greatly increases the obstacle presented 
to the enemy. 

428. To give both strength and durability, the 
scarp and counterscarp are revetted with walls of 
masonry which sustain the pressure of the earth, 
protect it from the effects of the weather, and, by 
their height and steepness, present an insurmount¬ 
able obstacle to an assault by storm. 

429. A fortification thus constituted would be 
sufficient for the protection of troops within it; but 
would not admit of exterior operations, because it 
affords no shelter beyond the ditch. Therefore, to 
procure the facility of manoeuvring on the exterior, 
a low work, in the form of a glacis, is thrown up a 
few yards in front of the ditch, and completely en¬ 
veloping it. The space between this work and the 
ditch is termed the covered-way , because it is cover¬ 
ed from the enemy’s view. 

430. The simplest form, then, of an effective pro¬ 
file for permanent fortification, consists of a covered¬ 
way ; a wide and deep ditch, with a scarp and 
counterscarp of masonry ; and a rampart, which, 
from its height and width, will give a commanding 
position to the parapet, and sufficient room behind 
the parapet for the necessary manoeuvres of the 
troops whilst in action. 

431. The general principles of permanent fortifi¬ 
cation, as now practised, are the results of centuries 
of experience in the attack and defence. The pro¬ 
blem presented for the solution of the engineer con¬ 
sists in making such a disposition of his works thal 


137 


no point within the range of their cannon shall af¬ 
ford a shelter to the enemy ; that they shal. enclose 
the greatest space with the smallest perimeter, with¬ 
out sacrificing the reciprocal protection of the parts, 
afforded by a flanking arrangement within the me¬ 
dium range of arms ; that no defensive dispositions, 
which can be destroyed by the enemy’s distant bat¬ 
teries, shall be exposed to their fire ; and finally, 
that the works shall be secure from an attack by 
storm. 

432. To satisfy these conditions, it was found that 
the space to be occupied must necessarily be enclosed 
by a series of bastions connected by curtains ; that 
the line of fortification must be continuous, and 
consist of a wide and deep ditch, and a high and 
steep scarp of masonry, to be perfectly secure from 
an escalade; and that the masonry of the scarp, 
which is the only part that can be destroyed by a 
distant fire, must be covered from this fire by the 
glacis of the work which forms the covered-way. 

433. From the range of the fire-arms that are 
used in the defence, it was found that the distance 
between the salients of the bastions should not ex¬ 
ceed four hundred yards ; and that for a reciprocal 
flanking arrangement, the length of the curtains 
should not be less than twelve times the absolute 
relief. 

434. To secure the work from escalade, experi¬ 
ence has fully proved, that the scarp w T all should not 
be less than thirty feet high, and that the top of it 
should not be above the crest of the glacis. 

435. With regard to the dimensions of the ram¬ 
part, they must depend on those of the ditch, and a 
suitable regard to that economy by which all human 
efforts are circumscribed. The width of the ram¬ 
part required for the free manoeuvres of troops has 


* 


138 


been fixed at about forty feet; and its height should 
give the parapet a command of at least twenty feet 
over the exterior ground. 

436. The dimensions of the parapet are the same 
as those for the profile of field works of the strong¬ 
est class. 

437. The fortification by which the space fortified 
is immediately enveloped, is termed the Body of the 
Place , or the Enceinte. It is seldom that a perma 
nent work consists simply of an enceinte, with its 
ditch and covered-way, particularly if some of its 
points are, from their locality, weaker than the rest. 
Other works are usually added to strengthen these 
weak points; they are termed Out-Works when 
they are enveloped by the covered-way, and Detach¬ 
ed or Advanced-Works when placed beyond it. 

438. The object of these works is to lengthen 
the defence, by forcing the enemy to gain posses¬ 
sion of them before he is able to make a breach in 
the enceinte 

439. The principal out-work is one in the form 
of a redan, termed the Demi-Lune, which is placed 
in front of the curtain. This work adds to the main 
defence by a cross fire on the bastion salients, which 
are the weak points of the enceinte, and when there 
are demi-lunes on adjacent curtains, the bastions 
between them are placed in strong re-enterings, 
thereby forcing the enemy to gain possession of the 
demi-lunes before he can penetrate, without great 
labor and loss of life, into these re-enterings. The 
main entrances to the work are usually through the 
curtains, which being the most retired parts are also 
the most secure; the demi-lunes also serve to cover 
these entrances, and to guard them from a surprise. 
This, at first, was the only use to which the demi¬ 
lune was applied; but engineers soon discovered 




139 


that, by enlarging it, new properties were developed, 
which at length caused it to be regarded as an in¬ 
dispensable accessory in the defence of weak points. 

440. The demi-lune, when of suitable dimensions, 
has also several other important properties, upon 
which it does not come within the scope of this 
chapter to dwell. Its ditch is sometimes on the 
same level with the main ditch ; sometimes it is 
higher; but in all cases the communications be¬ 
tween the two, and also with the demi-lune itself, 
are arranged so as to be easy and secure. 

441. Situated between the two flanks of the bas¬ 
tions, and directly in front of the curtain, a small 
low work, termed the Tenaille, serves to mask the 
scarp wall of the curtain and flanks from the ene¬ 
my’s batteries along the crest of the glacis. This 
mask is of very great importance, since, by pre¬ 
venting the enemy from making a breach in either 
the flanks or curtain, it will force him to make it in 
the face of the bastion; the flanks will thus be pre¬ 
served for the defence of the breach, and the enemy 
will not be able to turn the temporary, or permanent 
works, which may be constructed within the bastion 
to prevent him from gaining possession of the main 
work, by an assault of the breach, which he would 
be able to do could he effect a breach at the same 
time in the curtain or flanks. 

442. The covered-ways of the bastion and demi¬ 
lune form a strong re-entering at their point of 
junction, of which advantage is taken to arrange a 
small redan whose faces flank the glacis of the two 
covered ways. The space enclosed by this work, 
which is a part of the covered-way itself, is termed 
the Re-entering Place of Arms. 

443. The parts of the covered-ways in front of 


140 


the salients of the bastion and demi-lune, are termed 
the Salient Places of Arms. 

444. The places of arms are so called, because 
they serve for the assemblage of bodies of troops 
who are to act on the exterior. 

445. Small permanent works, termed Redoubts , 
are placed within the demi-lune, and the re-entering 
place of arms, for the purpose of strengthening 
those works. 

446. It is a received military principle, that the 
garrison of a work is no longer in safety, when it 
can be carried by storm, unless they are provided 
with a secure point of retreat. It is to effect this 
purpose that redoubts are constructed. The one in 
the re-entering place of arms secures the covered- 
ways from an attack by storm ; and that in the demi¬ 
lune forces the enemy to advance gradually, and 
with the greatest precaution, to gain possession of 
the breach in the demi-lune, and being provided 
with flanks, which, from their position, have a re¬ 
verse fire on the breach in the bastion face, the ene¬ 
my is forced to make himself master of it before he 
can venture to assault the breach in the bastion. 

447. Works, termed Interior Retrenchments, which 
have the same properties as a redoubt, are con¬ 
structed within the bastion. When the interior re¬ 
trenchment is sufficiently elevated to command the 
exterior ground, it is termed a Cavalier. 

448. The protection afforded by a redoubt to 
another work, is not by offering a place of safety 
into which the garrison of the work can retire when 
driven out of it; but in covering the retreat of the 
garrison by a warm fire, which will check the ad¬ 
vance of the enemy, and enable it to retire behind 
the redoubt, and not into it; for such an operation 
would inevitably create confusion in the redoubt, 


141 


and might jeopard its safety, as the enemy, in a hoi 
pursuit, might enter it pell-mell with the retreating 
troops. 

449. The crest of the glacis is broken into an 
indented line for the purpose of obtaining a flank 
and cross lire on the ground in front of the places 
of arms. 

450. Traverses are placed at intervals along the 
covered-ways ; they serve to intercept the projectiles 
which enfilade the covered-ways, and also to defend 
them foot by foot; enabling the troops to retreat 
from one part of the covered-way behind the traverse 
under the protection of its fire. 

451. The communications of the works consist 
of arched under-ground outlets, termed Posterns , 
of Ramps , and Stone Stairs. These communications 
are placed in the most secure parts of the works, 
so that the ingress and egress may be without 
danger. 

452. With regard to the relief of the outworks, 
as a general principle those most advanced should 
be commanded by those most retired. This princi¬ 
ple is applied in all the works, except the tenaille 
and the redoubt of the re-entering place of arms. 
The former must not mask the fire of the bastion 
flanks along the main ditch ; and the latter must 
not mask the fire of the bastion faces upon the 
glacis of the demi-lune covered-way. To satisfy 
these conditions, the two works must be com¬ 
manded by the demilune, which is more advanced 
than either of them ; but, by the process of defile¬ 
ment, they are both so arranged that the enemy 
will not have a plunging fire into them from the 
demi-lune. 

453. All the fortification, comprehended between 
the capitals of two adjacent bastions and the glacis. 


142 


is termed a Front of Fortification, or simply a Front . 
It is taken as the unit in permanent fortification. 

454. The usual method of effectually protecting 
any point, is by a flank fire; but, owing to the 
locality, or to some other cause, it may not be 
practicable to make a flanking arrangement; to 
supply its place, dispositions, termed Counterscarp 
Galleries, are made behind the counterscarp, with 
loophole defences for a reverse fire. This ar¬ 
rangement approximates the nearest to the military 
solution of the problem to see without being seen, 
since from the position of these galleries, the enemy 
will not be able to bring his batteries to bear on 
them, whilst they will present a formidable impedi¬ 
ment to all of his operations in the ditches. 

455. For seacoast defences, embrasures are made 
through the scarp wall, and the artillery is protected 
from shells by an arched bomb-proof covering over 
head. This arrangement is termed a Defensive 
Case-mate. This method of defence is only 
efficacious against a sea attack; for on the land 
side, where the enemy can approach regularly, 
case-mates would be immediately destroyed by his 
batteries, and the loss of life would be far greater 
in them than in an open defence, owing to the 
fragments of stone which each shot striking an 
embrasure would cause. 

456. Case-mates are also used simply as bomb¬ 
proof shelters for the troops and materiel; and no 
small fort indeed which can be bombarded is tenable 
without them. 

457. Attack. The measures for the defence 
resorted to in permanent works, are of a character 
‘o resist, with a certainty of success, multiplied 
attacks, with the most powerful means, if made 
openly. This certainty forces the enemy to provide 




















































. 





EXPLANATIONS OF PLATE XI 

Fig. 69. Shows a plan and longitudinal section of a Raft pre 
pared for a bridge; a are the logs of the raft; b cross 
pieces to confine the logs ; c sills to support and raise 
the bridge. 

Fig. 70. Shows a perspective elevation of a Flying Bridge, a a 
are the Boats ; b the Platform; c c the Uprights; d 
the Cross Pieces; e the Sliding Pulley for the cable ; 
f the Cable ; s s Buoys or Skiffs, for the cable to rest 
on. 

Fig. 71. Shows a perspective elevation of a Trestle ; a is the 
Uap or Ridge Beam; b the Legs ; c Cross Pieces 
to strengthen the legs. 

Fig. 72. Shows a Plan of a Regularly Fortified Front. 
a a, .. a is the Enceinte, or body of the place. 
b b the Bastions. 

c c .. c the Main Ditch, or ditch of the enceinte 
D D . . d the Bastion and demi-lune Covered-Ways. 
e e the Re-entering Places of Arms. 

F f f the Salient Places of Arms 

o the Demi-Lune. 

h the demi-lune Ditch. 

j the demi-lune Redoubt. 

t h the Ditch of the demi-lune redoubt 

M m the Redoubts of the re-entering places of arms. 

N n Ditches of the redoubts, 
a a . . a Traverses of the covered-way. 
o the Tenaille. 

Tig. A. Shows a Section of the enceinte, main ditch, and covered 
way of Fig. 72. 

A is the Rampart; of which a b is the Slope, and b c the 
Terre-Plein. 

b is the Parapet; of which c d e f g h is the outline, 
c is the Main Ditch. 

» the Scarp Wall. 

K the Counter-Scarp Wall. 

r the Embankment of the Covered-Way; of which m n is 
the terre-plein, n o p q the outline of the Banquette 
and Interior Slope, and q r the Glacis'. 


























































































































































143 

a large number of troops and materiel; and to 
approach the work slowly, and always under cover; 
making himself master of the exterior ground foot 
by foot, and proceeding forward only after having 
made such a disposition of his troops and works in 
his rear as to repel all the efforts of the garrison to 
delay his progress. This method is termed the 
Attack by Regular Approaches . 

458. A Siege is the operation of cutting off all 
communication with a work, and attacking by 
regular approaches. When the enemy confines 
his operation to a simple interruption of the com¬ 
munications, it is termed a Blockade. 

459. The operations of a siege may therefore 
be classed under two heads; those which are 
necessary to prevent all ingress to, or egress from, 
the work, and those which are required to gain 
possession of the work. 

460. The first class of operations comprehend 
the Investment , and the establishment of the Besieg¬ 
ing Army in intrenched camps around the work. 

461. The investment is performed by detaching 
a strong corps in advance of the besieging army, 
who, by a sudden movement, surround the work, 
and seize upon all the avenues leading to it. The 
object of the investment is to cut off all communica¬ 
tion with the work, and to secure everything with¬ 
out it that might in any way prove of service to the 
garrison. To effect this, the enterprise should be 
conducted with despatch and secresy; and the 
troops selected for it should be composed principally 
of cavalry and light troops, depending, however, on 
the character of the country; the number of troops 
being in proportion to the strength of the garrison, 
and the means that they can employ to oppose the 
investment. 


462. During the day-time, the investing corps 
will keep beyond the range of the cannon of the 
works, occupying the most favorable points to pre¬ 
vent excursions from them. At night the detach¬ 
ments will close in upon the work, so as to form a 
continuous chain of sentinels around it. Engineer 
officers, who accompany the investing corps, will 
make a complete reconnaissance of the work, and 
the exterior ground, for the purpose of facilitating 
the ulterior operations. 

463. In the meantime, the besieging army takes 
up its line of march, and arriving within the vicinity 
of the work, the different corps are distributed 
around it in camps, which are selected beforehand, 
beyond the range of the garrison’s cannon. The 
besieging army immediately proceeds to intrench 
itself, by throwing up works to prevent succors of 
troops,provisions, &c.,being thrown into the place; 
and also other works to restrain the excursions of 
the garrison. 

464. The first line of works, to prevent succors, 
is termed the Line of Circumvallation; the other is 
the Line of Countervallation. The first is usually 
a continuous line, as it is most suitable for the end 
in view; the second consists of detached works to 
cover the weak points of the camp, and particularly the 
parks of the engineers and artillery, in which all the 
siege train of these two arms are collected. These 
lines are about six hundred yards apart to leave room 
for the camps. 

465. The camps of the different corps are con¬ 
nected by removing all the obstacles between them, 
and opening communications for a free circulation 
of the troops, so that succor can be promptly des¬ 
patched to any point which is in danger from an 
attack by a superior force. 


145 


466. Whilst the lines are constructing, the engi 
neer officers are engaged in making a complete 
survey and plan of the work and its approaches; 
and in superintending the preparation of all the 
materials required for the construction of their own 
works, so that they may be carried on with vigor 
after they are begun. 

467. The object of the survey and plan is to 
enable the general, superintending the siege, to 
select the most suitable point to approach the work. 
This point is termed the Point , or Front of Attack. 
In selecting it, regard must be had to the strength 
of the point itself; the nature of the ground over 
which it must be approached; and the more or less 
ease with which the requisite materiel can be brought 
to this point. 

468. The salients are usually the weakest points 
of a work, because they are easily enveloped by the 
enemy’s approaches, and he will therefore be able 
to concentrate a heavy fire on them. Solid rock, a 
stony, or a marshy soil, present the greatest difficul¬ 
ties to the construction of the works of attack. And 
a good road, or navigable stream, affords the greatest 
facilities for the transportation of all the materiel 
required during the siege. 

469. The object of the besiegers being to gain 
possession of the point of attack, with the least 
sacrifice on their own side, the whole of their 
measures should tend to the attainment of this end. 
To effect this, the troops must be able to approach 
the work under shelter; its fire must be silenced; 
and a breach be made in its rampart. 

470. The works under whose shelter the troops 
approach the work attacked, are named Trenches 
(Fig. 73), of which there are two classes, the 
Parallels and the Boyaux. Each class consists of 

13 


a ditch, or trench, of uniform depth, and a parapet 
of uniform height, formed of the earth taken from 
the trench, and thrown up towards the work at¬ 
tacked. 

471. The parallel is a long line of trench, con¬ 
centric with, or parallel to, the works of the point 
of attack, which it envelopes ; and the boyaux are 
simply communications, in a zigzag direction, 
which lead to the parallel. The parallels and the 
boyaux both serve as a covered way, in which the 
troops can circulate with safety; but the boyaux 
are used exclusively for this purpose, whereas the 
parallels serve to contain troops who restrain the 
excursions of the garrison, and protect the work¬ 
men whilst carrying forward the approaches. 

472. The fire of the work is silenced, by select¬ 
ing suitable positions, near the parallels, from which 
the faces of the work can be enfiladed, and its guns 
be dismounted by a ricochet fire. 

473. The breach can be made when, the ap¬ 
proaches having arrived at the crest of the glacis, 
the scarp walls are exposed to breach batteries, 
constructed along this crest, which firing through 
the ditches of the work, batter away the scarp to 
its very foot. 

474. To lay out the trenches the alignement of 
the faces and capitals of the front of attack, as 
well as those of the collateral works, whose fire 
bears on the ground over which the approaches 
musrt be carried, are accurately marked out on the 
ground by stout pickets, and the distances from the 
most advanced salients to some point on their capi¬ 
tals are also determined. 

475. The object of procuring these alignements 
is to mark the position and direction of the trenches 
and batteries. The boyaux are run in a zigzag 


147 


direction across the capitals; because this is the 
shortest line to the salients of the work attacked, 
which are the points first reached ; and in this po¬ 
sition they are less exposed to the fire of the work, 
and are less in the way of the other works of the 
attack, than they would be if run on any other 
line. 

476. The position of the boyaux and parallels is 
laid out on the ground with pickets, to which cords 
are attached, or simply with pickets alone. The 
position of the First Parallel is six hundred yards 
from the most advanced salients ; it should embrace 
within its extent the faces of all the collateral works 
that protect the point of attack. 

477. At the distance of six hundred yards, the 
fire of the work is not very troublesome ; and it is 
within good range for a ricochet fire, if it be found 
necessary to erect the enfilading batteries near the 
first parallel. 

478. Boyaux lead from this parallel to points in 
the rear of it, about fifteen hundred yards from the 
work attacked. At these points all the implements 
and materials of the engineers are collected, and 
they are therefore termed the Depots of the Trenches. 

479. The approaches are begun by what is term¬ 
ed the Opening of the Trenches. The workmen 
are assembled at the depots, are supplied with in¬ 
trenching tools, and are marched and stationed along 
the line of boyaux, and that part of the first parallel 
which is to be first made. This is done just at the 
close of day; and troops, drawn up in order of 
battle, are stationed a short distance in advance of 
the workmen to protect them from the sorties of the 
garrison. The word is then passed along the line 
of workmen who commence opening the trenches, 


148 


which, from this moment,are pushed forward with¬ 
out intermission until the work capitulates. 

480. Whilst the first parallel is still in an in¬ 
complete state, boyaux. are commenced to lead from 
it to gain the position of the Second Parallel , which 
*,s laid out parallel to the first, and rather less than 
hree hundred yards from it; so that it may be still 
under the protection of the first, whilst in an in¬ 
complete state, should the garrison attempt a sortie 
Against it. The object of this parallel is to protect 
die approaches as they are pushed forward upon the 
salients. The same principle governs all the ap¬ 
proaches : <!hat is, they must be protected by a force 
superior to any that can be brought against them, 
and, in order that they may be succored in time, 
this force must be nearer than the garrison to the 
workmen employed in the trenches. 

481. The construction of the second parallel 
differs from that of the first, owing to the exposed 
state of the workmen to the grape shot of the 
work. To place the men under cover, as speedily 
as possible, the line of the parallel is marked out, 
by placing gabions side by side, and when these 
gabions are filled, they afford a protection from 
grape shot. 

482. With regard to the enfilading batteries, it is 
a disputed point whether they should be erected 
near the first or the second parallel. If the fire of 
the work attacked, is very warm and destructive, 
it may be necessary to place the batteries near the 
first parallel, to silence the fire of the work before 
the approaches can be pushed farther; but their 
effect, at this distance, is far less certain than at 
the second parallel, where every shot can be made 
to tell. 

483. Whatever may be the place of the batte- 


149 


r.cs, their direction will be perpendicular to the 
face enfiladed. The batteries will contain cannon, 
howitzers, and mortars. The cannon destroy the 
guns and their traverses; the howitzers annoy the 
covered-ways ; and the mortars throw shells into 
any part of the work which cannot otherwise be 
reached. 

484. The approaches are carried forward from 
the second parallel, so soon as the fire of the place 
is silenced ; but here the musket soon comes into 
play, a weapon of a more certain aim than cannon, 
and therefore more destructive to the workmen. 
The approaches are now given over to the engineer 
troops, termed Sappers, who carry forward the 
trench, termed a Sap, slowly, but with constant 
progress day and night. The sappers advance the 
end of the trench, working on their knees, and 
shielding themselves in front from the enemy’s fire, • 
by a large gabion stuffed with fascines, or wool, 
termed a Sap-Roller, which is rolled forward as 
they gradually advance. 

485. When the boyaux are completed to within 
sixty yards of the most advanced salients of the 
work, the Third ParaVel is commenced ; the pre¬ 
caution having been taken, however, to place Half 
Parallels, between the second and third, to protect 
the approaches until the third is completed. 

486. At the position of the third parallel, the be¬ 
siegers have arrived on the immediate ground of the 
work attacked. Here the struggle beg.ins to as¬ 
sume an attitude of equality. The attack loses its 
advantage of enveloping; it presents a front nearly 
the same as that of the defence; and shortly it be¬ 
comes itself the enveloped ; and then, if the re¬ 
sources of the garrison have not been entirely 
exhausted, each day will show but slight progress 

13* 


150 


on the part of the besiegers, who are confined to 
their trenches, and exposed to all the disadvantages 
of a commanded and enveloped position. 

487. After the completion of the third parallel, 
measures are taken to drive the garrison from the 
covered-ways, so that the breach batteries may be 
erected. This may be done in two ways ; either by 
still proceeding by gradual approaches, or else an 
attack by storm may be made on the covered way, 
and whilst this action is going on, the sappers es¬ 
tablish themselves along the crest of the glacis. 
The first method is slow, but certain, and accompa¬ 
nied with, comparatively speaking, but little loss of 
life. The second is rapid and more brilliant, but 
attended with great destruction of life, even in the 
most favorable cases, and is moreover seldom suc¬ 
cessful. 

488. All open assaults of permanent w'orks are 
attended with immense loss of life, and ought never 
to succeed where a garrison does its duty even with 
ordinary vigor. -This is a maxim justified by the 
results of every attempt of this character on record ; 
and it should never be lost sight of by the com¬ 
manding officer of the siege. Nothing but a case 
of the most urgent necessity, where a day gained 
may decide the fate of the besiegers themselves, 
should cover from obloquy any officer, whatever 
success may crown his order, who wantonly sheds 
the blood of brave men to attain an object, which a 
few hours’ delay would place within his reach, 
without perhaps the ioss of a man. 

489. To attack the covered way by storm, Stone 
Mortar Batteries are erected in front of the third 
parallel, for the purpose of throwing showers of 
stone into the covered-ways. A detachment of 
chosen troops is stationed in the third parallel, to de- 


151 


bouclie from it, at a given signal, and rush into the 
covered ways. The sappers are also in readiness, 
with their implements, to make the required lodg¬ 
ment on the glacis. When everything is prepared, 
a powerful tire is opened from the mortar batte¬ 
ries, and from all others, whose fire can reach the 
covered-way, to drive the besieged from it, and from 
their other defences near it. This shower of pro¬ 
jectiles ceases at a concerted signal, and the men 
composing the detachment rush from the parallel, 
and throw themselves into the covered-way, driving 
everything before them, and availing themselves of 
every defensible point in order to prevent the be¬ 
sieged from sallying out, until the sappers, who fol¬ 
low close on them, have had time to construct a sap 
within six yards of the crest of the glacis, around 
the salient place of arms of the demi-lune covered¬ 
way, into which they can retire for shelter from the 
covered-way. 

490. In the attack by gradual approaches, the 
sappers push forward the trench from the third pa¬ 
rallel, under the protection of the fire from the stone 
mortar batteries, proceeding directly on the salient 
of the covered-way, and when they have arrived at 
thirty yards from it, they extend the sap fifteen or 
twenty yards to the right and left, so as to embrace 
these salients, and throw up a mound of earth about 
ten feet high, from the top of which they can obtain 
a plunging fire into the covered-way, and thus pre¬ 
vent the besieged from occupying it. This mound 
is termed the Trench Cavalier. 

491. When the besieged are effectually driven 
from the covered-way, the sappers push forward the 
sap to within six yards of the crest of the glacis ; 
and they make a trench entirely around the covered¬ 
way, which is termed Crowning the Cove redr Way. 


152 


After the covered-way is crowned, breach batteries 
are erected around the salient places of arms, and 
from these positions breaches are made in the face 
of the demi-lune, and in the bastion faces. 

492. The besiegers now begin their operations 
to get at the breach, which is done by forming an 
underground gallery of frame-work and boards, 
leading to the bottom of the ditch; this is termed 
the Descent of the Ditch. From the bottom of this 
descent a trench is made, by sap, across the ditch, 
and up the slope of the breach to its top, where a 
trench encircling the top of the breach is formed; 
these operations are termed the Passage of the Ditch , 
and the Lodgment of the Breach. 

493. In some cases the breach is carried by as¬ 
sault, but the same objection is applicable here as in 
the attack of the covered way by storm. It should 
only be resorted to when the besieged show, by their 
efforts, that the lodgment cannot be otherwise ef¬ 
fected. 

494. If the demi-lune is provided with a redoubt, 
this work must be taken before the bastion can be 
carried, because it has a reverse fire on the breach 
from its flanks. A breach battery will therefore 
have to be erected in the demi-lune against the re¬ 
doubt, and when the breach is practicable, it may be 
assaulted at the same time as the bastion breach. 

495. Similar operations will have to be made 
against the interior retrenchments, in the bastion. 
Finally, at the breach in the last work the garrison 
must capitulate, or undergo, according to the custom 
of war, the fate of those who are carried by 3torm. 

496. Defence. The measures for the defence, 
although for the most part prepared beforehand, 
will in some degree be subordinate to those of the 
attack. The fortifications are here supposed in a 




EXPLANA1 IONS OF PLATE XII. 

Fig. 73. Shows a plan of the Works of Attack of a Permanent 
Work. 

a a . a the First Parallel. 
b b . b the Second Parallel, 
c c . . c the Third Parallel. 

»n .. d the Boyaux leading from the Depots of the 
Trenches to the First Parallel. 

E e . . k the Boyaux from First to Second Parallel. 

F f . . f the Boyaux from Second to Third Parallel, 
a g the Demi-Parallels. 

h h . . h Enfilading Batteries on the First Parallel 
11 . . i “ “ “ Second do. 

j j . . j Breach Batteries on the Glacis, 
o o . . o Trench Cavaliers. 
m m Bastions of the Front of Attack. 

N Demi-Lune of the Front of Attack, 
p p Demi-Lunes of the Collateral Fronts. 

Fig. B. Shows the general form of the Profile of the Trenches 
a is the Trench. 

B is the Parapet. 

c is a Berm, between the trench and parapet, that serve* 
as a banquette. 


Plate. I 




















































153 


complete state, and supplied with all the necessary 
provisions and munitions of war for a full garrison. 

497. So soon as any indications of demonstrations 
against the work are seen, everything on the exte¬ 
rior, within cannon range, which might afford a 
shelter to the enemy, must be removed. One gun 
at least, of long range, is placed in barbette on each 
salient of the enceinte and demi-lunes ; and at least 
two guns, loaded with case-shot, are placed in em¬ 
brasure on each flank of the enceinte. These are 
simply measures of precaution to guard against a 
surprise, and to prevent reconnoitring bodies from 
approaching the work. 

498. When the investment takes place”, the gar¬ 
rison will resort to every expedient of open force 
and stratagem to cut off the enemy’s reconnoitring 
parties ; and, finally, when hemmed in by the supe¬ 
rior forces of the besieging army, they will still 
watch every opportunity for annoying the enemy, 
by destroying his munitions, &c., without, however, 
jeoparding themselves, for they are now supposed 
beyond the reach of succors, and every life lost 
greatly increases the disproportion between their re¬ 
sources and those of the enemy. 

499. When all the preparations for opening the 
trenches are completed, the garrison will bring for¬ 
ward all its disposable artillery, and place it, in bar¬ 
bette, along the point of attack, this point having 
been ascertained by the movements of the enemy’s 
troops, the establishment of his parks, depots, &c 
Every night, about the presumed time for opening 
the trenches, fire-balls will be thrown out, to disco¬ 
ver the enemy’s movements; and when he com¬ 
mences his labors, a heavy fire will be opened on 
his laborers and troops, at the same moment from 
every point, and it will be kept up without intermis- 


154 


sion for some hourj. This is the moment that a 
select detachment of the garrison will sally out from 
the collateral works, and at a given signal the fire 
will cease, to allow them to charge the enemy’s 
flank. If this sortie succeeds, it should be vigor¬ 
ously followed up ; the workmen are dispersed, and 
during the confusion resulting from this, the detach¬ 
ment should, if there is the slightest prospect of 
success, endeavor to penetrate to the enemy’s parks, 
and destroy everything in their way. This is the 
only moment that a vigorous sortie can be made 
with any success. The parallels once established, 
the odds become too great against the garrison to 
justify another attempt, except great remissness is 
observed on the part of the enemy. 

500. The guns are withdrawn from the barbettes 
after the first night, and placed in embrasure on the 
most suitable points to retard the approaches ; they 
are also covered in flank by traverses. A fire, mostly 
of ricochet, is kept up on all the w T orks of the ene¬ 
my, at regular intervals, until he has advanced 
within the range of grape and musketry, when both 
of these projectiles are resorted to; the artillery 
being served with the greatest coolness, and the best 
marksmen with muskets or rifles, being stationed in 
the covered-w T ays. 

501. This system is persevered in, until the enemy 
gets on the glacis, or the immediate ground of the 
work. Then commences a system of petite-guerre , 
in which all means are taken to retard the work; 
sorties of a few picked men are continually made, 
to bayonet the sappers, and by throwing bags of 
powder, with slow-matches attached to them, against 
the sap-rollers, to blow them and the sapper up. 

502. Finally, the covered-w 7 ay is vigorously de¬ 
fended inch by inch, if attacked by storm, the troops 


i 


155 

retreating from it under the protection of the fire of 
the works in its rear. 

503. The defence of the breaches will chiefly 
depend on the measures of the attack; if these are 
by gradual approaches, the garrison will make fre¬ 
quent sorties from the adjacent works, in small bo¬ 
dies, on the passage across the ditch, whilst others 
attack the lodgment on the breach in front. But if 
the besiegers make their preparations to carry the 
breach by storm, the besieged should closely calcu¬ 
late the chances of opposing with the bayonet this at¬ 
tack. It is true that the military code, as generally 
received among nations, prescribes that the garrison 
should not accept terms of capitulation until they 
have sustained at least three assaults of the breach. 
But neither duty nor honor requires a brave man to 
sacrifice himself, when, all prospect of succor or of 
retreat being shut out, he finds himself in position, 
face to face, with ten to one against him, and en¬ 
tirely at the mercy of his enemy in case of defeat. 

504. A breach can only be defended with a cer¬ 
tainty of success, and without jeoparding the lives 
of the entire garrison, when a redoubt or interior 
retrenchment is in its rear, under the cover of whose 
fire the troops, placed at the breach to watch the 
enemy’s movements, and delay his progress, can 
retreat with safety. When this measure of security 
is provided, the troops at the breach should use 
every human means, short of attacking with the 
bayonet, to prevent the enemy from advancing, and 
they must not retire before there is an appearance 
of imminent danger to the point of safety, from the 
enemy entering it pe'l-mell with the retreating de¬ 
tachment. 

505. In a general summary of the ordinary 
march of the attack and defence, and the applica* 


156 


tion of the principles of permanent fortification, no 
allusion has been made to accessory measures of 
defence, which often furnish both parties with the 
most powerful resources, as mines , the uses of 
water , cfc.; since these measures are not of uni- 
venal application, owing to their requiring suitable 
localities for their employment; and they would, 
moreover, require explanations and details, which 
none but the professional engineer would probably 
understand, and which would offer no interest to any 
other. 

506. Uses of permanent works. The subject of 
national defence is one which presents itself with 
such strong claims to the careful consideration, not 
only of the statesman and soldier, but of every 
private citizen, as all have the deepest interests at 
stake, in the settlement of so momentous a question 
as the safety of the State, that a few words seemed 
called for on the part which permanent works play 
in the military organization of a frontier; and the 
relations subsisting between their action and that 
of other means of defence. 

A thorough discussion of this subject would em¬ 
brace too wide a field to be brought within the 
present scope of the writer ; for to do full justice to 
it, he would be obliged to enter into the develop¬ 
ment of the principles of other branches of the mili¬ 
tary art in some respects foreign to the purposes of 
this essay. But there are a few reflections of too 
striking a character to be suppressed, and which 
the events recorded, not only in the history of for¬ 
eign nations, but in that of our own country, must 
bring forcibly home to the breast of every thinking 
person. 

To defend the utility, the indispensable necessity 
of the military organization of a frontier with per- 


157 


manent works, were to cite the experience of every 
people, of every age, who have been exposed to the 
disasters of invasion, whether upon their land or 
maritime frontier. Poland, owing to the want of 
such an organization, fell a victim to the greatest 
political crime of modern times. Spain had well 
nigh been ensnared in an insidious attempt against 
her existence as an independent nation, of as dark 
a dye as the dismemberment of Poland, when the 
heroic resistance of Saragossa, and a few other 
fortified places, gave her people time to recover 
from their first surprise, and enabled them to rally 
under the protection of their strongholds, and or¬ 
ganize that system of determined resistance, that 
“ war to the knife,” which at length freed their 
soil from the pollution of a foreign master’s foot¬ 
steps. France saw her naval power annihilated, 
and her commercial marine literally swept from the 
seas, by the loss of a few naval pitched battles ; 
and whilst the fleets of her enemy rode in triumph 
at her very threshold, slept on in unbroken secur¬ 
ity, under the guns of her sea-board defences. At 
a subsequent period, when, overwhelmed by the 
united forces of Europe, her hitherto victorious 
armies were driven within their own territory, it 
is the opinion of able military men, that a few 
strongholds on the flank of the enemy would have 
enabled her great Captain, who contended with his 
usual genius against such unequal odds, to have 
retrieved her fortunes, whilst that enemy rushed on 
to seize her open unprotected capital, and after¬ 
wards trembled in its possession at the thought of 
a reaction in the people. 

No intelligent person, it is presumed, could be 
found, in the present advanced stage of military 
icience, to advocate a system of defence with ac* 

14 


158 


tive forces alone, whether land or naval. The 
perishable nature of such armaments, the casualties 
to which they are exposed, the uncertainty of the 
issue of pitched battles, all point to some other 
means of defence, which, by prolonging the contest 
on one or more points, will increase the chances of 
retrieving any mishaps. To defend an open fron¬ 
tier of any nature, without the aid of permanent 
works, requires the display of a large moveable 
military force, whose ultimate expense, long expe¬ 
rience has but too amply proved, increases in a ra¬ 
pid proportion with the undisciplined character of 
the troops. This is the opinion of military men of 
all nations; and the testimony of our generals, 
whether of the militia, or of the regular army, goes 
to show, that whatever reliance may be placed on 
the valor and patriotism of our militia in times of 
emergency, still it is necessarily the most expensive 
force that can be brought into the field against an 
enemy, owing to the losses which are necessarily 
incurred by the employment of men totally unac¬ 
quainted with the economy of a regularly organized 
army. This being the case, and the nature of our 
political institutions being such as to render a resort 
to a large standing army dangerous to their exist¬ 
ence, it behooves us to devise some means by which 
the smallest regular force may be called for in de¬ 
fence of the State, and in which the militia may be 
employed, not only in the most efficient manner for 
the defence, but also most economically. 

The best means, it seems to the writer, by which 
this can be effected, consists in a judicious organi¬ 
zation of the frontier, with permanent works of such 
strength as each particular site may require. The 
defence of these works may be safely left to gar¬ 
risons principally of militia; and as thi e arm of our 


159 


national defence is composed of the most valuable 
members of society, this kind of service will be 
most appropriately intrusted to it, as it is less one¬ 
rous to the individual than that of the field, and is, 
moreover, attended with less destruction of life, both 
from the diseases incident to the exposure of the 
camp and the casualties of pitched battles. 

As to the class of permanent works which would 
be required for an efficient organization of our fron¬ 
tier, the writer does not feel himself called on to 
give an opinion, as this is a point which ought to be 
settled alone by a board of competent engineer offi¬ 
cers. Without permanent defences, both our land 
and sea-board frontier would be left open, not only 
to the temporary inroads of an enemy’s armies and 
fleets, but, as was seen during our last war with 
England, positions could be selected, and perma¬ 
nently occupied by him during the war, from which 
our entire coast might be kept in a state of con¬ 
tinued alarm, whilst great detriment might be caused 
to our coasting trade, and to the line of the sea¬ 
board, from occasional marauding parties and small 
cruisers. With permanent works of a proper cha¬ 
racter at suitable points, the most of these evils 
would be obviated; our harbors would be secured, 
and our large roadsteads, with even the extensive 
estuaries for which our coast is remarkable, could 
be effectually closed against an enemy’s squadrons. 
These strongholds would serve as places of resort 
for our own vessels of war, when in less strength 
than those of the enemy, where they could lie in 
security, and watch for a favorable moment of ac¬ 
tion. They would serve as covering points for our 
fleets, in event of any disaster happening, either 
from battle or from tempests. They would form 
the natural rallying points for floating batteries 


160 


moved by steam, by means of which the enemy 
would at all times be kept on the alert, and his posi 
% tion at any point far beyond the range of the guns 
of the work, would be rendered insecure, and in 
most cases, untenable, except at a great risk. In 
our land operations, these fortified points would play 
anything but a passive part, if properly combined 
with moveable forces. In the hands of a skilful 
general, their part, on the conti ary, would be emi¬ 
nently active. They might be made to cover, not 
only their own garrisons, but large bodies of troops 
which might take up an unassailable position under 
their guns, and be in readiness at all times to oppose 
the enemy in front, if of equal force, or to attack 
his flank or rear, if he attempted to treat them with 
neglect. They might be made to serve as points of 
safety, upon which the garrisons of weaker works 
could retreat in case of necessity, or from which 
they could obtain succor if strongly pressed by a 
superior force. It is in this way that permanent 
works become truly formidable to an enemy, and 
enable us to guard distant points bt yond the range 
of their cannon, without placing a man, or a gun, 
for the immediate defence of those points. 


NOTE A. 


Manner of determining the proportion between th( 

terre-plein of a Square Redoubt , the developmenl 

of its interior crest , and the size of its garrison. 

Fig. A. 

g Let a b c d (Fig. A.) be 
the line of the interior 
crest; a b c d that of the 
foot of the banquette slope ; 
f the outlet through the 
parapet; and e the interioi 
traverse. 

Representing by x, the 
number of yards in the 
^ side a b, the side a b will 
be equal to x diminished by twice the distance be¬ 
tween a b and a b, which distance may be taken on 
an average at 9 yards; the area of the square b c, 
or of the terre-plein, will then be represented by 
(x— 9)2. 

Let the following notation be adopted :— 

x, the side of the square A B. 

y, the number of the garrison. 

r, the reserve taken from the garrison. 

n, the number of ranks on the banquette for the 
defence. 

s, the area of the terre-plein occupied by a bar¬ 
bette in the salient. 

14 * 

















162 


s', the area occupied on the terre-plein by the 
powder-magazine. 

s", the area occupied by the traverse, and the 
passage in its rear. 

Z, the number of yards on the interior crest for a 
barbette in the salient. 

V, the width of the outlet f in yards. 

Now, as the area allowed for each man is one and 
a half square yards, we shall obtain the following 
equation, to represent the relation between the terre- 
plein, the garrison, &c. 

(*—9)2= 1,50 y+ *+<?' +a"; .... (1) 
this is termed the equation of the interior space. 

As each man occupies one lineal yard along the 
interior crest, we obtain also, 

4* = —+/+/';.(2) 

n 

which is termed the equation of defence, as it ex¬ 
presses the relation between the development of the 
interior crest, the remainder of the garrison after 
taking out the reserve, the number of ranks for the 
defence, and the length of the interior crest required 
for the cannon in barbette, and for the outlet. 

To show the application of the equations (1) and 
(2), let it be required to find the side of a redoubt, 
and the number of its garrison, which shall be de¬ 
fended by two ranks on the banquette, after taking 
out a reserve of one-third of the whole number, and 
have a barbette in each salient. 

By a calculation, easily made, it can be shown, 
that each barbette will occupy about 75 square 
yards of the terre-plein; a powder magazine for 
four guns, 20 square yards ; a traverse of earth, 
with the passage between it and the foot of the ban¬ 
quette, about 180 square yards ; or, if of timber, 
about 50 square yards; the portion of the interior 




163 


crest for each barbette will be nearly 18 lineal 
yards ; and that for the passage about 4 lineal 
yards. 

Taking Eq. (2), and making the substitutions re¬ 
quired by the conditions of the Prob. we obtain, 


4* = y — -i^ + 4 + 72; 

and from it, 

y — 12 * — 228. 

Substituting this value of y in Eq. (1), and 
placing for s, s', s", their values, we have 
(x — 9)2 = 18 x — 342 -f 300 + 20 + 180; 

or, 

(X — 9)2 = 18 x + 158 ; 


from which, by solving the equation, 

x = 38 yards; 
consequently y = 228 men ; 


and r = 76 men. 



MOTE B 


Manner of equalizing the Excavation of the Ditch t 
and the Embankment of the Parapet. 


Fig. B. 



Let the following notation be adopted, Fig. B. 

V, Volume of the embankment. 

S, Surface of its profile. 

I, Line described by the centre of gravity of S in 
generating the embankment. 

V', S', and l ', corresponding values of the ditch. 

Now, from the centre-baryc principle, we have 
V = S Z; . . (1), and V' = S'Z'; . . (2). 

But as earth, when freshly thrown up, occupies a 
greater volume than in its natural state, if this in¬ 
crease be represented by the fraction m , we shall have 
to represent this condition 



and eliminating V and V', by means of these three 
equations, there results 









165 

or the value of the surface of the profile of the ditch 
in known quantities. 

Representing now by 

x, the width of the ditch = a d; 

y, its depth = a e ; 

a , the angle of the natural slope of the earth with 
the ground = a h e. 

We obtain 

a h = y Cot. a; 

and for the bases of the slopes of the scarp and 
counterscarp, 

eb=iah = fy Cot. a; and cg = jah = Cot. a. 

we then obtain for the area of the trapezoid abed, 
which is S', by subtracting the surfaces of the tri¬ 
angles a e b, and c g d, from the rectangle a g, 

S' = x y —(g y 1 Cot. a + i y 1 Cot. a) ; 
or, S' = x y — y 2 Cot. a; . . . (5) 

an equation from which either x or y may be ob¬ 
tained, by assuming either the width or the depth. 
But as x has certain limits, from the nature of the 
Prob., we will solve Eq. (5) with respect to y, and 
will obtain, 

y = ° Tan. a ( x —>/ ar* — l s’ Cot. a ,) . . (6) 

We observe here, in the first place, that the radical 
expression admits only the minus sign before it, be¬ 
cause x and y are decreasing functions of each 
other; that x u cannot be less than l S' Cot. a , other¬ 
wise the expression will become imaginary; and 
when it is equal to it, the profile of the ditch becomes 
a triangle, so that the minima limits of x will be, 

x=y/l S' Cot. a; and x = 12 feet; (Art. 39.) 

and the maximum value will be found by multiply¬ 
ing the height of the interior crest by the denominar 




166 


tor of the fraction which represents the superior 
slope, and subtracting«,from this result the horizontal 
distance between the interior crest, and the crest 
of the scarp. (Art. 34.) 

Any quantity, therefore, which is greater than the 
minima limits, and less than the maximum, will 
satisfy the conditions of the Prob., if it gives for a 
result y -between 6 and 12 feet. (Art. 39.) 

But should the value of y not fall between these 
limits, then we shall be obliged to change the form 
of S; and consequently find a new value of S'; 
making it greater or smaller, as the case may re¬ 
quire. 

To show the manner of applying this formula to 
practice, let it be required to find the dimensions 
of the ditch of a square redoubt from the following 
data; the command of the interior crest is 8 feet; 
the thickness of the parapet 9 feet; the superior 
slope l-6th ; the angle of the natural slope 45°; and 
the tread of the banquette 4 feet. 

Taking, in the first place, Eq. (4), 

a very simple calculation will show that -jj will be 

very nearly represented by the fraction f, for re¬ 
doubts between 20 and 40 yards of a side, measured 
along the interior crest, l' being the middle line of 
the top of a ditch, which is a mean between the 

least and greatest limits. The value of m is, in or¬ 
dinary earth, about J, and varies generally between 
i and I 1 ,, so that, by substituting these values in the 

Eq., we have 


S '=K-8TT)S = lS; 




167 


and the value of S, calculated from the data, being 
122 square feet, we have 

S' = 81, square feet nearly ; 
substituting this value of S' in Eq. (6), we obtain 
y = j (x — s/ x* — 189); 

from which we see that x*= 189, gives x= 13 feet, 
therefore the quantity assumed for x must be greater 
than this ; if then, we assume x= 15 feet, and sub¬ 
stitute it in this formula, we obtain 

y = * (15 — V 225—189) ; 
or y =7 (15— 6) = 7.7 feet; 

which satisfies the required conditions. 

It may be added, that with this width of ditch, the 
line of fire passes 2.6 feet above the counterscarp 
crest. 

In the foregoing calculations, no allowance has 
been made for the volumes of the barbettes ; and the 
traverse when of earth. To make this allowance, 
Eqs. (3) and (4) will have to undergo a suitable 
modification, as follows :— 

The cubic contents of each barbette, in a salient, 
is nearly 140 yards; and that of the traverse about 
*70 yards. If, then, the total cubic contents of all 
the barbettes, and the traverse, be represented by 
V", a given quantity, Eq. (3) will become 
V + V" = V'+i y, . . . (X); 

and 

SZ + V" = S'Z' + i S'Z', . . . (Y); 

Mow, as V" is a given quantity, it can be repre¬ 
sented by S" Z, in which S" is found by dividing 
V" by Z; making this substitution in Eq. (Y), we 
obtain 

Sr=s ( s + s ") if Gr+r) * • * • 





for the modified value of S' Eq. (4), to suit this 
case. The operations for finding x and y, Eq. (6) 
are the same as already shown. 

The calculations here given suppose the plane of 
site sensibly horizontal, and the interior crest paral¬ 
lel to it; when this is not so, as, for example, in a 
defiladed work, the volumes of the parapet and ditch 
will have to be calculated for each face separately. 

The method of doing this, where the site is very 
irregular, consists in making an unequal number 
of parallel profiles, on each face, at equal distances 
from each other, and finding the area of each pro¬ 
file, and then using the following notation and for¬ 
mula, 

71 -p 1 

let s', s", s'", siv,.s , represent the 

areas of the successive profiles, their entire num¬ 
ber being n + 1 ; 

Z, the distance between the profiles; 
v, the volume between the extreme profiles; then 

_ l / n n+l\ 

v ~ 3 \s' + 4s"+ 2s"' + 4s IV + 2s v .. .4s+s /* 

In other cases, where the site is not very irregu¬ 
lar, a mean profile may be found, and the Eq. (Z) 
be used. 

It is usually best, since the dimensions of the 
ditch cannot be uniform throughout, to adopt a uni¬ 
form depth, and to vary the width as circumstances 
may require. 






























































